Some TMNT stuff really isn't for little kids.
He is the oldest, wisest and most cautious Turtle, the one who always plays by the book. He also bears the great burden of being the team's chosen leader. Leo is dedicated to perfecting his ninjutsu skills and will stop at nothing to defend his brothers and the entire city. Wearing a blue bandana, with katanas holstered on his shell, Leo firmly believes it's his ninja duty to protect all people.
- Named after Leonardo Da Vinci
- His weapons were bestowed upon him by Splinter due to the Turtle's sharp mind and steely resolve
- Oldest of the 4 Ninja Turtles - considered the "big brother"
- Bears the burden of the responsibility of his brothers and sensei
- The hardest worker, studier and trainer
Leonardo has a faded scar running from the right side of his forehead to his right cheek. He wears wooden armor on his chest resembling a Yoroi samurai armor's chest plates. He also has shoulder pads and a samurai skirt, besides custom made Japanese footwear. There are Japanese characters painted blue on the back of Leo's shell.
Like his brothers, Leonardo started out as a small turtle hatchling being used for scientific research in the laboratory of Eric Sacks. He was regularly injected with mutagen that gave him increased strength and healing.
After April O'Neil freed the Turtles and Splinter, they began to rapidly grow in size and intelligence, both of which were comparable or greater than that of humans. For the next fifteen years Leonardo spent most of his life in the sewers with his brothers and adoptive father, where he was taught the art of ninjutsu. His preferred weapon was the katana, which he showed considerable and versatile skills with (even able to expertly slice up a pizza with it in mid-air).
He had a noticeably closer relationship with Splinter than his brothers did right from the start of his life, often addressing him as "Dad" rather than just "Sensei." Because of his greater maturity and sense of responsibility, Leonardo was appointed the team's leader, although this often caused clashes with Raphael.
Along with his brothers, Leonardo fought and defeated a squad of Foot Clan warriors who were about to execute hostages at a subway. He did so despite his reservations at disobeying Splinter. When they were found and photographed by a now-grown April O'Neil, Leonardo intervened to keep Raphael from unduly intimidating her, but still threatened vaguely to find her if she told anyone about them.
Upon learning of what happened, Splinter ordered the Turtles to bring April back to their lair, where Leonardo was surprised to hear of April's part in their origins. However, they were interrupted by an attack from the Foot Clan, which April had unwittingly led there, and Leonardo fought to defend his home and his family. However, he was repeatedly electrocuted by the Foot Clan, and was forced to surrender when the Shredder threatened Splinter's life. From there, he was captured along with Donatello and Michelangelo and taken to Sacks' mansion.
Along with Donatello and Michelangelo, Leonardo nearly died when the blood was drained from his body in order to harvest the mutagen, but he was able to break out of his cage when April administered a massive dose of adrenaline to all three Turtles. Newly energized, they rejoined Raphael and set out to stop Shredder from detonating a chemical weapon in the heart of New York. However, they were hampered by another attack from the Foot clan, in which Leonardo was again electrocuted, knocked out and eventually went over a cliff.
Like his brothers, Leonardo had limited success fighting against Shredder individually, but led the way in a tag-teaming "buck buck" attack that allowed them to overwhelm the armored villain. When the toxin-filled spire was destabilized by Shredder, Leonardo ordered them to keep the tower from falling using their bodies. They were unsuccessful, and barely managed to survive the subsequent fall to the ground.
Having reclaimed some of the mutagen, he and the other Turtles headed back home and were able to heal Splinter. He later met up with April again, more relaxed and at ease now that they knew she wouldn't reveal their secret.
Two years later, Leonardo found himself in conflict with Michelangelo and Raphael over the secretive natures of their lives. While Raphael resented their unappreciated status and Michelangelo longed to be a part of the human world, Leonardo attempted to remind them that the human world would never accept them, and that their place was in the shadows as ninja.
When the brothers set out to stop Shredder from escaping from a prison convoy, Leonardo sat beside Donatello in the front seat of their garbage truck, where he was involved in unleashing some of the weapons like a katana-throwing arm. When Shredder was teleported away, Leonardo took this as a personal failure as a leader, though Splinter told him that there was nothing he could have done.
Shortly afterwards, Donatello informed Leonardo of the properties of the purple ooze that had transformed Rocksteady and Bebop. Not only could it turn humans into mutants, but if reengineered, would allow the four brothers to become human (at least in appearance). Leonardo immediately rejected the idea, and swore Donatello to secrecy, not realizing that Michelangelo had been eavesdropping on the entire conversation.
After Michelangelo told Raphael, another fight broke out between the brothers as Raphael was angered that Leonardo would keep such vital information from his brothers, and Leonardo was adamant that they were Turtles and would remain that way. He left Michelangelo and Raphael behind while he and Donatello investigated a break-in at the museum, and discovered that Shredder was planning to use a device to open a portal to another dimension. On the way home, they received a distress call from Michelangelo, and attempted to intervene at police headquarters, but ended up exposed to the police.
Angered that Raphael had taken such risks and gotten April in trouble, Leonardo vented to Splinter that he couldn't get the disparate personalities of the Turtles on the same page. Though Splinter told him that their different personalities were strengths to the team, his frustration mounted after their mission to Brazil failed, culminating in him declaring that they were brothers, but were not a team.
Upon returning to New York, the Turtles were faced with a difficult decision, where the purple ooze and becoming human in appearance seemed to be the only way to stop the Technodrome. Leonardo deferred to his brothers, saying that he would go along with whatever decision they made. Raphael smashed the purple ooze, reinforcing that they were and would remain Turtles.
Instead the Turtles offered an alliance to Chief Rebecca Vincent, in order to stop Krang from assembling the Technodrome over New York and taking over the world. Leonardo fought Krang along with his brothers, teaming up with Raphael to rescue Michelangelo from the alien's formidable robot body. Their efforts led to the Technodrome and Krang being sent back through the dimensional portal.
Along with his brothers, Leonardo was given a key to the city in front of the NYPD, but chose to remain a secret from the larger world. He told Chief Vincent that April would be able to get ahold of them, should the police need them again.
- Splinter and the Turtles were laboratory experiments, much like in the IDW comics origin story.
- Leonardo's face is based on both Russell Crowe and Nelson Mandela.
- Johnny Knoxville voiced Leonardo for the first film, but didn't voiced him in the sequel,because he wasn't invited back.
- In the first film the turtles are 15 years old, as the video footage April watches is dated 1999, and Eric Sack's mentions that he's spent the last 15 years trying to replicate the results from the lab, thus making them 15 years old in the first film. And since "Out of the Shadows" takes place two years later, that would make the turtles 17 in "Out of the Shadows".