Leonardo, often referred to as Leo, is one of the main protagonists of the 2012-2017 television series and the leader of the Ninja Turtles. He is also the oldest of the four brothers, who all share a home in the underground sewers of Manhattan, New York City. The adoptive son of Master Splinter and the younger adoptive brother (and love interest) of Karai, Leonardo belongs to a diverse family consisting of three other mutant turtles who are his younger ninjutsu birth brothers: Donatello, Michelangelo, and Raphael; and the ratlike Splinter, who serves as the Turtles' adoptive father and sensei. Due to his persevering dedication towards ninjutsu, as well as his level-headed discipline, (and partly because he asked for it), Splinter chose Leonardo to be the leader of the Turtles. Leo is an enthusiastic ninjutsu prodigy, who wears a royal blue headband, and fights with (and wields) two twin katana swords called Niten Ryu. He leads the various missions of the Turtles. Like previous incarnations, he is named after Leonardo da Vinci, and is known for being secretly enamored with his older adoptive sister and the antagonist-turned-protagonist Karai/Hamato Miwa (who is also Splinter's long-lost birth daughter).
In this latest version, Leonardo seems to be more experienced and still perfecting his fighting skills and leadership abilities to make more solid decisions and gain more trust from his three younger brothers. He devises tactics and gives orders. He regularly watches an animated science fiction show called Space Heroes (a parody of Star Trek: The Animated Series) and uses it as a guide for his leadership skills, often attempting to quote from the show in an attempt to sound intimidating and heroic, even if most of his attempts fall flat due to him sounding overly cliché.
Being the eldest and most mature of the four, he is the fearless leader of the Ninja Turtles. In the aftermath of Splinter's passing, he reluctantly stepped up to the increasingly difficult role as sensei, which adds an even more stressful burden on his shoulders. Since the episode "The Deadly Venom", he is the only Ninja Turtle who is capable of using the spiritual, healing abilities of "the healing hands" technique to heal himself and others which enshrouds his body in a white aura by chanting the mantra and the right hand seals.
This version of Leonardo was originally voiced by Jason Biggs from the series premiere until Season 2 Episode 19, temporarily recasted by Dominic Catrambone for the last 7 episodes of Season 2 (nonetheless, his voice still sounds very similar) and finally replaced by Seth Green from Seasons 3 to 5. With Green as Leo's newly recent (and final) voice actor, Leo's voice becomes much deeper. His change of voice is explained by the character having wounded his larynx (vocal cords) in the aftermath of the battle in the Season 2 finale.
Upon the sudden demise of his adopted father and master, he reluctantly steps up as sensei in addition to being leader, which makes his life even more stressful and hectic than ever. He is visited, on occasion, by the spirit of Splinter who encourages him to lead his family and friends to stopping new evil threats, such as Kavaxas.
Leo is an emerald green colored anthropomorphic mutant turtle ninja warrior. His eyes have sapphire blue irises with black pupils, but like his brothers when they are shown fighting or being stealthy, they disappear, leaving his eyes white (similar to the 2003 incarnation). He wears a royal blue bandana mask (though he wears a black bandana in Broken Foot and Owari) where the tails length range between Donnie and Mikey's. Leo is the most skilled fighter, and he doesn't have much changes to his physical appearance like all his previous incarnations, except for the fact that his green skin is slightly darker than the others. His height ranges between Raph and Donnie's. His ninja gear includes brown knee pads and elbow pads, and beige rolled bandages wrapped around his wrists, ankles and fingers. However, unlike previous incarnations, Leo's hands have two fingers and a thumb (like his brothers).
The theme song states that he "does everything it takes to get his ninjas through". In other words, he makes the commands which sometimes bothers his brothers especially Raphael. During an interview, Jason Biggs described Leo as "the glue who holds his brothers together and tries to keep them in line, saying things like 'Come on, guys! Focus and concentrate!' since he's a born leader who is very protective of his family." He has proven several times already that he will make a rash decision, including his choice to spend time with Karai instead of help his brothers. He also faces constant challenge from his own insecurity, barely managing to face his confidence issues to fight off mutant fungi threatening the entire city.
The 2012 incarnation showed Leonardo as his typical self, retaining many of his developed character traits. His leadership qualities are ever-present (though several times already in the show’s short life, they’ve been the cause of much strife for the turtle), he maintains a strong dedication to his training, and he’s always fighting to protect his brothers’ lives. However, this time his achievements and struggles make sense, because the “teenage” part of the turtles is actually worked into the story.
The leader of the Turtles, Leonardo aspires to be a brave, decisive, perfect hero. Unfortunately, he's an inexperienced teen (for the moment at least) with three smart-aleck brothers. It's the gap between his aspiration and current situation that is the greatest source of frustration in Leo's life. He's the most driven of the four Turtles, training and studying relentlessly. He tends to be hard on himself, but his diligence does not go unnoticed; he is the favored student of Splinter, whose approval he very much craves.
An adventurous, courageous, responsible, hardworking, protective, self-serving, honorable, righteous, respectful, level-headed, prudent and enthusiastic ninjutsu prodigy with a "can-do" attitude, Leonardo is the most serious, disciplined, cool-headed mature and focused of the team. Being the designated leader of the group, Leonardo is very enthusiastic about his role. He is also a big science-fiction fan (or "nerd" as referred to by his brother Raphael). His favorite series is Space Heroes, while his favorite character from the show is Captain Ryan. Leonardo has a habit of memorizing Captain Ryan's best lines from the show and sometimes repeating them during battle. Leonardo is so caught up with Space Heroes that he relies on Ryan's character traits more than on his own intuition, which often causes his brothers (especially Raphael) to question his leadership.
For the most part, he tries to be the mature and responsible sibling, but there are occasional times where he can be as childish as his brothers, such as teasing Donatello for losing to a mutant monkey and trying to be like an unrealistic TV character, although Leonardo often tries to comfort his brothers when they are scared or upset, mostly Michelangelo. His attempts to appear strong can also backfire as he makes rather cliché or ridiculous statements while trying to intimidate his enemies, such as introducing the team as the 'Mighty Mutants' or 'Turtles of Justice', while trying to appear heroic, or telling a scientist experimenting on a monkey that they'd had enough of him 'monkeying around'. Raphael often expresses his lack of patience for these quips.
He (along with the help of Donnie) comes up with most of the team's plans and strategies, while he and his brothers are fighting bad guys or training in the Lair, but while these strategies have proven to be effective, his lack of practical experience has prompted his brothers - particularly Raphael - to become frustrated with his approaches, and they try to do things their own way instead. Sometimes, due to his oppressive burden as leader, Leonardo faces the fear of losing his brothers, though he is often calmed down by Splinter, who claims that the fear is held by almost all leaders.
He has a lot of responsibility on his hands, which can sometimes overwhelm him. He watches a T.V. Show called "Space Heroes" and wants to be just like the captain he sees on T.V. Overall, Leo acts as a big brother to the turtles and as a teacher's pet to Master Splinter. He was chosen to be the leader because of his willingness not by his skill. Leo is the most mature out of all his brothers, aside from Donnie, always acting like a guide and sometimes even a parent to his brothers. He is very protective of his siblings and is willing to do anything for them. Unlike all his incarnations, Leo is somewhat a sci-fi geek, aside from Donnie. Though Donnie is more of a techy geek. Leo loves "Space Heroes" and tends to try to be like the hero on there, much to the annoyance of his brothers. He also tries too hard to act like a hero and says cheesy lines, which annoy Mikey, Donnie and Raph. He is the wisest, most experienced and balanced of the team and demonstrates many important qualities needed in a leader. Leo does his best to lead the team, but he sometimes second-guesses himself and his constant sibling rivalry with Raphael can cause problems for the team and puts a strain on his relationship with Raph. He often tries to compare himself to the main character of "Space Heroes", Captain Ryan, which annoys his brothers. Like other incarnations, Leo is a perfectionist.
Leonardo is shown to be openly selfless, courageous, and self-serving, and shows it when it counts. In the Season 1 Finale, this is especially shown in Showdown, Part 1 and Part 2, where he almost sacrifices himself twice to save his brothers and the entire world. In the Season 2 Finale, The Invasion, Part 1 and Part 2, Leonardo leads the Kraang away from his brothers and finds himself facing off against the entire Foot Clan alone. Knowing the dangers they'd face, he doesn't contact his brothers for help.
Fifteen years before Rise of the Turtles, Part 1, the benevolent Hamato Yoshi purchased four baby turtles. Yoshi came into contact with a rat and had to fight against a couple of Kraang. The aliens dropped their mutagen causing the mutation of Yoshi and the turtles. Yoshi raised the turtles as his own children and continues to train them in ninjutsu.
Leonardo and his brothers were once ordinary turtles: when they were infants, they were adopted from a pet store by Hamato Yoshi. When their soon to be father walked passed a strange man, a Kraangdroid, he felt something odd about him and followed. Unfortunately, Yoshi gave away his position when he accidentally stepped on a brown rat's tail. The Kraang found him and attempted to kill him, but Yoshi fought back hard. In the end, the Kraang dropped the canister of Mutagen they were holding, causing the turtles and Yoshi to mutate. Yoshi, having to have stepped on that rat, thus mutated into a humanoid brown rat by the name of "Splinter", while Leo and his brothers, after coming in contact with Splinter when he was human, mutated into humanoid turtles. Splinter knew they would never be accepted in their urban society, so he took them to the sewers, made a home down there, and made the four turtles his children. Knowing the world would be dangerous and there would be a time where they want to explore the outside world, Splinter trained the boys in the art of Ninjitsu. Leo and his brothers were named after great Renaissance artists from a book Splinter fished out of the storm drain.
Skills, Powers and Abilities
Leonardo is the most stern, serious, focused, disciplined, responsible and among his brothers, being able to take on much larger opponents quicker and more easily in addition to coping with hectic stress.
- Leadership: Leonardo's bravery, determination, and willpower make him a great leader. In the beginning, his only flaws as a leader were due to his lack of experience (mostly due to his teenager status). His immaturity was also causing him to occasionally make impulsive decisions that might make the situation worse, as well as his brothers sometimes not obeying his orders, and a desire to be a hero that results in him making rather poor taunts in battle. His most significant fear is to let the team down and fail as their leader. However, as he and his brothers continued to fight against the Shredder and his forces, Leonardo becomes more focused and disciplined as a leader, even becoming willing to sacrifice his own life for the sake of others. He's also able to make difficult choices whenever the situation came down to it. A note to make is that Splinter believed that Leo was destined to become the leader of his brothers ever since he was a small boy.
- Kenjutsu: Leonardo is a highly skilled martial artist and master swordsman. Leonardo was trained by Splinter in Japanese sword fighting. As his signature weapons are his twin katana, he is highly skilled in the sword fighting style of the Niten Ichi-ryū,(二天一, "two heavens as one"), making him an excellent swordsman. He makes use of his katana swords for skilled offense and defense, allowing him to slice through the metal of the Kraangs' robot bodies (stabbing and dismembering them), deflect shuriken. His skills with his swords enable him to fight against powerful and skilled members of the Foot Clan including Tiger Claw, Karai (until she discovered the truth about her origin), and even The Shredder, able to push him back even slightly during their fights.
- Tantōjutsu: Aside from his swordsmanship Leonardo is also skilled with a tantō. Whenever he finds himself without his either of his katana, Leo can take the tantō from the handle of one of them and use it for self-defense.
- Kyūjutsu: Leonardo also possesses aptitude in archery and uses a yumi and arrows to fight long-ranged.
- Shurikenjutsu: Leonardo can throw shuriken with remarkable accuracy.
- Enhanced Strength: Leonardo is the second strongest of the turtles, as he was shown to be beaten by Raphael during their scuffles and training sessions. However, he is stronger than Donnie and Mikey (as seen in Mousers Attack! where he and Raph consider themselves as the two strongest fighters). Leo possess above average strength that gives him an advantage in a fight. Not only is he able to deliver powerful blows with his physical attacks, but he is able to throw heavy objects (including people) over his head. He is also able to knock back and hold his own against larger and/or physically stronger opponents.
- Enhanced Speed: Leonardo is able to move at great speed, able to free run on rooftops without losing momentum. He also possesses great reaction speed, allowing him to dodge projectiles such as lasers the Kraang's blasters, and enemy attacks. He can also spin swing twin katana at incredible speed as well. Despite being a turtle, he is not slow. He can run fast enough to avoid laser fire from a Kraang weapon. He can also move things at enhanced speeds too, like twirling his katana blades.
- Stealth: Being taught by Splinter, Leonardo,as well as his brothers, are able to be one with darkness and hide and move within the shadows without being noticed. Like his brothers, he is stealthy, can hide in the shadows, sneak around without being detected, and use hand to hand combat like a real ninja.
- Retractable limbs into Shell: Though rarely (if ever) depicted, he has retractable limbs and the normal ability of a turtle to retract his head and limbs into the safety of his shell.
- The Healing Hand/Healing Factor: In the events of The Deadly Venom, Splinter taught Leonardo a unique ancient secret art and healing technique known as the Healing Hand. With the technique, Leonardo is able to heal himself and others, and even remove Karai's venom from his body despite there being no known cure for it. According to Splinter, he shows great gifts as a healer, and that being at the edge of his life had given him "a power that few martial artists can tap." His healing factor seem to work while in water, where he woke up after being ambushed by the Foot Clan during the Kraang Invasion 3 months later but the fight left him injured.
- Intelligence: He has a good line of defense, and is the best at planning strategies. In most episodes, he's highly capable of improvising the objects around him to his advantage.
- Improvising: In most episodes, he's highly capable of improvising the objects around him to his advantage. Which is essential to his leadership abilities especially when he's on constant pressure.
- Stamina and Endurance: He shown off his high stamina in The Invasion, he was able to handle and stay much alive while the long Foot-Bot challenge, he was also able to defeat all of Shredder's henchmen, but all that work worn him out giving Shredder the chance to finish him off.
His signature weapons of choice here are purely dual twin katana (刀) swords, which he uses and fights in the Niten Ryu (also known as Niten Ichi-ryu "The strategy of two heavens as one") style of kenjutsu, making him a skilled and excellent swordsman (although referred to as katanas, Leonardo's swords are actually much more closely modeled around the "Ninjatō" (忍者刀 ninjatō), (also known as ninjaken (忍者剣) or shinobigatana (忍刀)), a fictional sword similar to the katana, depicted as being a ninja's version of the weapon. It is usually straight-bladed, has a square guard, and is shorter than katana. . The handles have the same dark red and gold color that Raph's sai and Mikey's nunchucks have. Unique from his brother's weapons (Bo-Staff, Sai, and Nun-Chucks) Leo's weapons are the only ones specifically designed to deliver killing blows, though Leo is much too honorable to want to do so. You know what they say,"two swords are better than one."
In this incarnation, he's still very much learning to be a master swordsman (especially when compared to the 4Kids Leonardo). However, he's showing encouraging signs of it.
It's is implied that Leonardo has multiple identical katana swords stashed at the lair, such as when he is shown returning to the Turtles' underground lair after a fight with only one katana (having lost the other katana during the brawl) but is later shown with two katana swords sheathed on his scabbards.
Typically, Leonardo wields a pair of katana; one Daitō (大刀), a catchall word for the larger sword in a daishō pair (the word itself refers to the length of the blade, which was usually 70-90 cm) and one Shōtō (小刀) or Kodachi (小太刀), a catchall word for the shorter sword in a daishō pair. ("Kodachi" can also be used to refer to a blade that was similar to a wakizashi, but designed to be used by itself rather than in combination with a katana.), which, like his brothers with their chosen weapons, he is highly skilled with.
In Pulverizer Returns, Splinter says that the boys are getting too reliant on their own weapons, which makes them swap. After this process, Leonardo is left with Donatello's bō staff. During a fight, the turtles become uncooperative with their new weapons and swap back. When Splinter finds out, he takes away all weapons, stating that anything can be useful in battle. When Leonardo and his brothers are trying to save Timothy, Leonardo uses a metal pipe, which he holds and fights with it in a style similar to his katanas. In Turtle Temper and The Gauntlet, he also used a Yumi bow and like the rest of his brothers wields shuriken.
The handles of his katana blades also double as holsters for smaller tanto knives, as seen in The Manhattan Project, Part 2 and the season 2 finale, The Invasion, Parts 1 and 2, when he was battling the Shredder's minions.
When fighting a mind-controlled Raph in Clash of Mighty Mutantanimals, he shown a proficient use with a spear.
During his time in space during the first half of Season 4, Leonardo used a pair of space katana blades and a laser blaster created by Fugitoid. In the Season 4 finale and the Season 3 episode "Vision Quest", he was shown to fight with a bow and arrows.
Throughout much of the fifth and final season, Leonardo used a new, different type of swords (O-katanas) as his main weapon (the same ones he used in Season 4 episodes Broken Foot and Owari) in which the blades are longer and narrower with curved edges (the handles of his new O-katanas are black, as apposed to the typical red-and-gold colored handles), after shattering his original sword in an attempt to strike the evil demodragon Kavaxas. In the 4-episode Monsters vs. Mutants story arc Leo is given a wooden stake-shooting gun by Renet.
- Splinter- Leonardo's surrogate father and sensei. Like all of his incarnations, Leonardo is the most loyal and the closest towards his sensei, as he always takes Splinter's advice seriously, even though at times, his stubbornness starts to annoy Splinter. Also, Leonardo gets confused whenever Splinter uses difficult words of wisdom while giving away his advice, but he always takes it under consideration. Leonardo was devastated at Splinter's death at the hands of Shredder in Annihilation: Earth!, Part 2. Throughout season 4, he communicated with holograms of his master and when the turtles returned to earth he was quick to warn Splinter of Shredder's betrayal which saved him. Reunited with his master, Leonardo was eager to catch up on his adventures in space with him after he was curious. However, when Splinter died permanently, Leonardo stayed at his grave the longest out of everyone once more sad at his loss.
- Karai - It is also shown that during their first encounter, amid their sword duels and fencing challenges, Leonardo developed secret romantic feelings for Karai from the moment they first met, even though she is his adoptive sister by Splinter; she was taken in by the Shredder after her mother's death and was corrupted by his tyranny ever since: tasked with destroying her birth family (including Leo) before changing sides upon discovering her true heritage as his adopted sister, Leonardo eagerly wants to be able to trust Karai, even after it became apparent that she has repeatedly mistreated and backstabbed him and his friends. He still finds a special bond with Karai, though knowing that she is Master Splinter’s lost daughter gives him more reason to fight to save her from Shredder’s control. Raphael disapproves of Leonardo's association with Karai, considering Karai a threat to their survival and Leonardo a liability for so frequently giving Karai the benefit of the doubt. Leonardo's ambiguous friendship with Karai was frayed when he tried to kill Shredder, and Karai revealed to him that Shredder was her father. Leonardo was the first family member Splinter confessed to that Karai was actually Hamato Miwa, his daughter.And, of course, Leo cares for his brothers much more. In one episode, Leonardo sternly informed Karai that if she wanted to fight, she should fight him. He also said if she went after his brothers or Splinter, he would even go as far as hunt her down and finish her off himself. This sentence indicates that he can be very courageous and daring, even going as far as slaying the love of his life and would do so if necessary without hesitation. Despite all this, Leonardo truly cares about Karai and, in addition to rescuing her from peril, does try to inform the truth about her life to her multiple times. However, Karai flatly distrusts and harshly rebuffs him until she sees it herself (whilst sneakily scheming an ambush by leading Tiger Claw to the Turtles' lair after treacherously deceiving to Leo by pretending to believe him about Splinter, much to Raphael's ire). After finally (and genuinely) realizing the truth herself, Karai became Leonardo's trusted ally, adoptive sister and love interest reciprocating his thoughtful empathy, growing closely affectionate to Leonardo. After Karai was captured again, Leonardo unsuccessfully tried to save her from falling into a vat of mutagen, which turned her into a feral snake mutant. After many hardships and dilemmas, the duo rekindle their relationship with a much healthier bond (as seen in the Season 4 finale, and much of Season 5) where Karai appreciates Leonardo for finishing the Shredder, something she couldn't do. Relationship-wise, Leonardo's attachment to Karai is two-fold: he is in love with her and has also come to consider her part of his family since she is the biological daughter of his adoptive father Hamato Yoshi.
- Raphael - Leonardo has a love-hate relationship with his second younger brother Raphael. He and Raphael argue the most amongst all of the turtles, especially concerning who should lead the pack. However, they share deep respect for one another. In Showdown, Part 1, it is shown that Raphael is very protective about Leonardo and cares deeply for his brother, just like Leonardo does for him. It is seen that the two trust each other more than the others as seen how they often discuss things privately away from the others such as Leonardo's issue with Karai. As the series progresses, Leo's rivlary with Raph softens, and when crucial moments come, the two save each other.During the end of Season 2 and early Season 3, Raph became more sympathetic towards Leo.
- Donatello - Leonardo's third youngest brother. Of all the Turtles, Leo and Donnie rarely squabble (unless absolutely necessary). In fact, the duo get along very well out of all the Turtles because they share many common traits, but they occasionally tease each other throughout the series (i.e. Donnie pesters Leo about having a crush on Karai). Leo usually gets anxious whenever Donatello completes an invention, one after the other, fearing that Donatello's technology might go wrong at one point. Furthermore, Donnie relies too much on modern technology and high-tech gadgets instead of traditional ninjitsu moves (such as from feudal japan). Additionally, Leo can get quite annoyed by Donnie's book-smart technobabble and be jealous when Donnie outsmarts Leo, acting like a know-it-all. Such as the time where Raph hits Donnie for doing so and Leo points out his satisfication. Vice versa, Donnie sometimes doubts Leo's leadership, but eventually shows gratitude towards his big brother. They rarely ever argue, but in The Gauntlet, Leo was yelling at him for not expecting a very complicated mutagen bomb, got mad at Donnie for taking off to battle the Kraang in Rise of the Turtles and getting annoyed at him for teasing him about Karai. Leo, along with Raph, also didn't seem to think highly of Donnie and Mikey as much as a strong fighter, as seen in Mousers Attack, where he considered it unfair that him and Raph were paired up against their little brothers in a fight which caused tensions between them. He even got in Donnie's way when they were battling the purple dragons and made him and Mikey go after April's phone while they dealt with the mousers, and to add insult to injury he and Raph kept labeling both younger brother the B-team. Though he soon regrets not getting Donnie nor Mikey's help when him and Raph are being attacked by the mousers. In the end, Leo gives Donnie and Mikey new found respect as fighters when they defeated the mousers and recoils his relationship with Donnie, and Mikey. In the Season 2 finale, Leo and Donnie entered a falling out over how to stop the Kraang invasion, with Leo suggesting that they pack up their valuables, abandon the sewers and leave the city, while Donnie insisted on holding their ground, staying at the city and fight them off with the Turtle Mech, despite the fact that his invention was still under construction. During the 3rd episode of Season 5 (Heart of Evil), Donnie's resentment against Don Visiozo endangered the Turtles' mission, once again creating another falling out between the two brothers, who eventually reconcile by the end of the episode. Despite all of these fallouts, Leonardo and Donatello forge a strong brother/best friend relationship.
- Michelangelo - Leonardo's youngest brother. He and Michelangelo don't fight, unless Michelangelo's slight dimwitted nature irritates Leonardo, causing him to criticize Michelangelo's idiocy. Whenever Leonardo goes through a plan, he occasionally questions Michelangelo to see if he's really listening. Leonardo also feels very protective of Michelangelo, saving him from danger several times. (i.e. Showdown, Part 2, or Follow The Leader, when Leonardo actually goes back to save Michelangelo from danger.) Leonardo was even surprised at Michelangelo's change into a serious warrior in Into Dimension X! and seemed slightly jealous at his taking leadership. They worked quite well together to acquire a worm to cure Karai. Overall, their brotherly-best-friend bond is unbreakable.
- April O'Neil - Leonardo's first human friend. He saves April from the Kraang as seen in the first two episodes of the first season: Rise of the Turtles, Part 1 and Rise of the Turtles, Part 2. They are very good friends, and April was the one Leonardo sought out when searching for advice regarding his crush on Karai. Leonardo's friendship with April is somewhat similar to a brother/sister relationship, when one looks after the other, like when April called for Leonardo to save her from the Creep in Within the Woods, and when Leonardo gives her hope in seeing her mother again in Buried Secrets.
- Casey Jones - Leonardo's second human friend. He met Casey in the eighth episode of the second season: The Good, The Bad and Casey Jones. Leonardo often calls Casey for help and Casey would come to help out. While they barely interact, they remain good friends.
- Leatherhead - Though they are allies, Leonardo and Leatherhead are almost never seen interacting, apart from fighting the Kraang. Leatherhead seems to interact more with Donatello and Michelangelo.
- Slash: Leonardo and Slash are allies, but not good friends. Leo views Slash with suspicion and distrust since the events of Slash and Destroy, while Slash is easily antagonized by Leo and prefers not to work with him. Nevertheless, Slash considers Leo a role model in his own efforts to be a good leader to the Mighty Mutanimals, and finally admits this to Leo at the end of Battle for New York, Part 2 and Leo apologize to Slash for distrusting him in the first place and the two make amends at the end of the episode.
- Timothy - Leonardo never interacted with Timothy (the Pulverizer) as much, but he always gets annoyed whenever the Pulverizer tries taking too many risks that could get him injured or even killed (The Pulverizer Returns!).
- Shredder - Leonardo's arch-nemesis. Out of all the turtles, Leonardo seems to be the one who has interacted with him the most. He is most aware of Shredder's moves among all his brothers, but still fails to fight him well. Shredder is much more experienced at ninjutsu and has more skills that Leonardo almost always fails to recognize, but Shredder only fails to kill Leonardo and his brothers, as they keep on escaping to the Sewers of Manhattan, NYC. Leonardo was the one who ended Shredder’s life by putting an fatal blow on the villain.
- The Kraang - Leonardo's targeted enemy. Relationship is unknown.
- Baxter Stockman - One of Leonardo's archenemies. Leonardo tends to forget Baxter's name (examples: "Dexter Backsman", "Daxter Boxman", "Blister Speckboy", etc.).
- Fishface - One of Leonardo's enemies. Relationship is unknown.
- Rahzar- One of Leonardo's enemies. It is a thought that he is worried about Michelangelo battling him. When they find out that Michelangelo is in danger, he says that they have to save him. He was the one who cut the ropes off Michelangelo and then pats him on the head.
- Leonardo is named for the famous Renaissance master, Leonardo da Vinci.
- Leonardo's name is Italian, meaning "Strong as the Lion/Lion-Bold".
- His name in Katakana is レオナルド (Reonarudo).
- Niten Ryu ("Two Heavens Style"), is described as Leonardo's weapons, but it is in fact the name of a fighting style for Japanese swords, and not a weapon. A two-sword set-up is properly known as a daisho, (大小). Niten Ryu, instead, is short for Niten-ichi Ryu, (二天一流), a two-sword style developed by legendary samurai Miyamoto Musashi.
- Leonardo's swords, whilst being referred to as "Katana", are actually "Ninjatō" (忍者刀 ninjatō), (also known as ninjaken (忍者剣) or shinobigatana (忍刀).
- The existence of the ninjaken has been up for debate for many years.
- Leonardo's swords, whilst being referred to as "Katana", are actually "Ninjatō" (忍者刀 ninjatō), (also known as ninjaken (忍者剣) or shinobigatana (忍刀).
- According to the Concept Art of Leonardo's Katana, "Niten Ryu", one sword is longer than the other, and a Tanto blade is concealed within the hilt of the "Daito" (Long Sword), and a "Kogatana" (Mini Tanto) is concealed within the Saya's (Scabbard's) binding wrappings, all as secondary, auxiliary weapons to his Katanas.
- His mastery of Ninjutsu includes: Seishin teki Kyoyo, Taijustu, Qigong, Kenjustu, Shurikenjustu, Kayakujustu, Shinobi-iri, Sui-ren, Boryaku, Kyuudou, and Intonjutsu.
- Leonardo seems to be the most educated (out of the four brothers) about Japanese culture and etiquette:
- He understands Japanese when spoken to and is able to speak in this language to some extent.
- He knows, at least basics, of Japanese etiquette (i.e. he bows to Master Splinter) as first seen in "Rise of the Turtles, Part 1".
- His caller ID on April's phone is "ichiban turtle", which means "number one turtle".
- He is the oldest of his brothers; the remaining age order is Raphael, Donatello and Michelangelo.
- Of all the turtles, he's the most mature:
- He was made leader by Splinter's choice.
- He sometimes acts like a parent to Michelangelo.
- He argues with Raphael, and eventually finds logical reasons to win the argument.
- Donatello and Michelangelo tend to listen to Leonardo instead of Raphael, because he thinks first before taking action.
- Unlike his brothers, Leonardo always takes Splinter's advice seriously.
- Leonardo has a tanto blade hidden under his wrist wraps, as seen in "TCRI".
- Like all of his incarnations, except for the 1987 series (fear of snakes), Leonardo's greatest fear is failure and losing his brothers.
- This version of Leonardo stores his swords on his back much like the original Mirage one, side by side instead of crossed.
- When Leonardo's voice actor was changed between seasons two and three, it was explained in-show as being the result of damage to his larynx during his battle with the Foot Clan in "The Invasion, Part 2".
- Since then, he was hence forth and for the duration of the series voiced by Seth Green.
- His favorite show is Space Heroes.
- He is right-handed.
- According to his concept art, Leo loves watching Saturday morning cartoons.
- Leo is first seen without his mask in "Within the Woods" when all his gear was removed to help him heal better after he was beaten down hard by the Shredder.
- He is also the third turtle to be seen maskless.
- Leo is also the first turtle to be seen without his gear.