Raphael rescued Spike after he was flushed down into the Sewer. Spike's favorite food was lettuce leaves and was frequently seen chewing on a leaf. Raphael had a soft spot for Spike and often talked to Spike about the important parts of his life in private. This was important for Raph, as he needed Spike as a sounding board for his inner-thoughts and feelings. He could not reveal his feelings to his brothers because he doesn't want to seem "soft" to them, so he shared them with Spike, who could not speak at the time, but was an excellent listener. His brothers sometimes teased him about this. Raph often played with Spike and cooed at him, as well as allowing Spike to ride around on his shoulder, frequently using his pet for personification.
As mutations work by combining the DNA of the one being mutated with the DNA of the last animal, plant or human they have been in contact with, Slash got his human attributes from Raphael who got his from Splinter.
Raph was in the kitchen alone, speaking intimate with an unseen other person. Raph acknowledged the other person was worried about him, and admitted he was about to enter a dangerous new situation. But Raph reassured the other person that he would come home safe, and said "I love you man." The camera revealed the other person to be Raph's unmutated pet turtle Spike, eating a lettuce leaf. Raph was alarmed to hear his brother Michelangelo saying "awww" behind his back. Mikey asked if Raph was talking to his pet turtle, but Raph nervously denied it, then angrily told Mikey to shut up. When Mikey declared how adorable the situation was, Raph became enraged and ran after him.
Raph had recently become a liability in a battle against the Kraang because he stopped to argue with Vic after he had used insults to easily provoke Raph to anger. Raph went to the kitchen with Spike to blow off steam, asserting that his anger makes him a better fighter. Craving validation, Raph asked Spike to chew on his lettuce leaf to show he understood. Raph was startled when Splinter snuck in unannounced, having listened to Raph's rant. Splinter wanted to tell Raph a story, but Raph declined. Splinter used Spike against Raph, asking the pet turtle to chew on his leaf if he wanted to hear the story. Spike did so, and Splinter went on to tell Raph about his past with Tang Shen and Oroku Saki.
One of the mutagenic experiments in Donatello's lab exploded, sending projectiles into the living room that destroyed random objects. Spike was standing on a small crate, and Raph leapt into danger to rescue Spike just before the crate was destroyed. After ensuring Spike was safe, Raph angrily confiscated Donnie's mutagen canister and took it and Spike into his own bedroom. Raph was called back out into the living room to clean up the mess, but the door slam knocked over the canister which popped open and spilled mutagen on Raph's floor, Spike watched the mutagen spill out and with an inspired look made his way to the Mutagen. While Raphael was ranting and raving about the explosion being Donnie's responsibility and thus there was no reason of him even having to be there helping clean up the Mess, before being silenced by Splinter who pushed a pressure point on Raph's shoulder, Spike was mutating. When Raph returned to his room, he found Spike was now a talking seven-foot mutant turtle. Spike—now preferring to call himself Slash—was as dedicated to Raph now as he ever was, and they agreed to become partners. What Raph didn't realize was that Slash's fresh mutation also made his mind unstable, and he quietly made plans to kill Leonardo, Donatello and Michelangelo so that Slash could have Raphael all to himself. Raph and Slash went out on their own to locate other mutagen canisters, as Leo, Donnie and Mikey went out separately to do the same thing. Slash discreetly grabbed Donnie and savagely beat him, taking his purple mask as a trophy. Mikey caught up with Raph and Slash, frantically telling Raph that Donnie was missing, but also shocked to meet a new mutant turtle who turned out to be Spike. Slash insisted that Raph not worry about his brothers and continue looking for mutagen with him, but Raph informed Slash that his brothers would always come first. Slash angered, and Raph watched in horror as Slash started knocking Mikey around no less savagely. Raph intervened, knocking Slash away from Mikey. Slash told Raph he didn't want to fight, and asked him to stand back and let him finish off Mikey. Raph was disturbed when he realized the kind of person Slash had become. When Slash refused to relent, Raph threw a smoke bomb in his race and made off with Mikey. Raph and Mikey finally found Donnie, confirming that it was Slash who had attacked him. As Raph stopped to treat Donnie's wounds, Mikey was called away by Leo's voice, only to find that it was Slash impersonating Leo. Slash proceeded to thrash Mikey as badly as he had previously beaten Donnie, taking Mikey's orange mask as another trophy. Raph found Mikey seriously injured, and demanded to know why Slash was doing this. Slash told Raph that his brothers were holding him back and were unneeded. Slash didn't want to fight Raph, but knocked him away to grab Mikey to finish him off. Raph rejected what Slash had become and called him a monster. Raph's rejection pained and enraged Slash, who finally attacked Raph head-on, denouncing that Raph was as foolish as his brothers. Slash gained the upper hand, leaving Raph all but beaten, and Slash prepared to finish him off. Mikey and Donnie tried to intervene, but were easily beaten down, giving Raph enough time to get back up. Raph informed Slash that friends protect each other, and that Raph would prefer to be more like his brothers. Raph and Slash continued to fight, and they fell through the ceiling of the little girl's bedroom while Leo was trying to convince her to give him the mutagen canister she had in her possession. The three turtles left the girl's bedroom, and Raph and Slash took their fight back to the rooftops. Slash insisted that he and Raph were the same kind of warrior, but Raph said the difference between them was that Slash was pure evil. Slash unleashed his greatest rage on Raph and almost killed him when Leo intervened. Leo stopped to ask Raph about the new turtle, but Slash used this distraction to assault Leo from behind—something Slash had wanted to do for a long time. Raph took out a small knife, preparing to fight Slash to the finish. Slash seemed pleased to see this as a reminder that the two of them are powerful because their anger makes them strong. But hearing this reminded Raph of Splinter's lesson from before, and Raph skillfully pressed a pressure point on Slash's arm to partially paralyze him, taking the opportunity to grab the trophy masks which Slash had tied around his arm. As Slash writhed from the pressure point, he lost his footing and started to fall off the edge of the rooftop. Raph, still loving Slash after all this, scrambled to save him from falling, but was unable to reach him in time. But when Raph looked to see where on the ground Slash had fallen, Slash had already gone. Raph mourned Slash's loss; this did not go unnoticed by Splinter, who counseled Raph on how to cope with the loss of loved ones. Slash felt deeply betrayed by Raph's rejection, a hurt that would persist even after his post-mutation insanity wore off.
Slash appears as one of the detained mutants in the Kraang prison. He was seen threatening one of the Kraang droids shortly before a mind control chip was planted on his forehead, putting him to sleep. After Metalhead freed all of the mutants, Slash proceeded to destroy a large number of the Kraangdroids, including one that was about to shoot Raph. Slash gave Raph an affirmative nod before escaping on his own. This was the first hint that Slash's post-mutation insanity had finally passed.
Slash returned and teamed up with the Newtralizer, the two having escaped another Kraang prison together. Slash and Newtralizer made an oath together to destroy the Kraang; furthermore, Slash quickly latched onto the Newtralizer as a brother figure to fill the hole left when he became alienated from Raph. Slash and the Newtralizer attacked and annihilated a Kraang convoy to steal some plutonium to power their personal teleportation devices. Later, Slash spotted Raph and Casey from the rooftops and pursued them—not to attack them, but to see if Raph missed him, and to meet Raph's new partner. Raph introduced Slash to Casey, but Slash cynically asked if Raph was going to betray Casey too. Slash also told them about his new partner the Newtralizer, cautioning them to stay out of their way. This encounter confirmed that Slash was no longer psychotic, but also how much Raph's rejection had hurt him. Later, Slash and the Newtralizer argued over the use of the Kraang Walker they planned to hijack; Slash worried about harming innocent humans, but the Newtralizer could care less about them. When the duo arrived at the docks, Slash kept the Kraangdroids distracted while the Newtralizer took control of the Walker. The Newtralizer was careless with the Walker, almost crushing Slash under its giant foot, but Slash was quickly saved by Raph; it genuinely surprised Slash that Raph would save him but realized that Raph would always be there for him. The Newtralizer started using the Walker to attack Kraang and turtles indiscriminately, but Slash climbed the Walker to speak to him, reminding him that the turtles also fight against the Kraang. The Newtralizer didn't care about this, and Slash realized just how depraved his partner really was. Slash used his morning star to pin the Newtralizer inside the Walker's cockpit, declaring an end to their partnership. The Newtralizer tried to shoot Slash, but Raph hit the Newtralizer's weapon with his shuriken. Slash, Raph and the other turtles were trying to escape the Newtralizer when Casey showed up, launching one of his hockey puck detonators inside the Walker's machinery. The Newtralizer used his personal teleportation device to escape as the explosion destroyed the Walker. Raph and Slash took time to reconcile, and Raph invited Slash to come home, but Slash felt it would be better if he remained alone. Slash said amicable goodbyes to the turtles and Casey before teleporting away, leaving Raph sad that Slash was gone again.
Slash returns leading his own formed team the "Mighty Mutanimals", which includes Pigeon Pete, Dr. Tyler Rockwell, Jack J. Kurtzman (as their noncombatant benefactor) and Leatherhead. They first appear when the turtles are outnumbered by the kraang who manage to find and capture two humans that they prepare to mutate who the turtles save and rescue. They then take them to meet Jack at an abandoned factory; not knowing that the kraang are following them along the way. Once there, Jack informs them all that they must work together to stop the kraang's plan which it to launch a giant rocket into the earth and mutate the entire planet in the process. the two teams are sceptical about working together; given their past history. Suddenly the kraang [along with some Biotroids break in and attack them [while injuring Jack in the process]. They all then retreat back to Antonio's Pizza-Rama where they realize that they must put aside their differences and work together to save the world after Jack fives them a intel disc about the kraang's plan and tells them to do so. Slash and the Mutanimals then attack the Kraang (including Kraang Subprime who survived from his supposed death in The Invasion, Part 1) as a distraction for the turtles. Despite their best efforts, Kraang Subprime manages to launch the rocket. Luckily the turtles (who use Donnie's new invention, the Turtle Blimp) reset the coordinates of the rocket to the sun and escape by using their gliders. After the Kraang retreat, both teams celebrate their victory. They then head to TCRI to save the populace of New York City and possibly the rest of the world.
Slash and his team break into TCRI to where the room that contains the portal is located and start to fight the Kraang. Luckily they manage to open the portal to Dimension X in order for the turtles to enter and rescue the mutated humans. Suddenly more Kraang including Mrs. Campbell along with some Biotroids and Irmabots show up and ambush them. Unfortunately they are all captured in the process and the Kraang deactivate the portal which leaves the turtles trapped on the other side. They are then placed in a glass cell, but Dr. Rockwell (who uses his telekinesis abilities) manages to free them all and they begin to attack the Kraang again. They then open the portal again and contact the turtles (while destroying the various Kraang robots in the process). They then help the turtles succeed in retro-mutating the humans and teleporting them all back to Earth. They then teleport the turtles back to Earth as well after they give them their coordinates. They then appear with the turtles on some rooftops after saving the city (with its power restored, the kraang gone and all of the humans free, normal and returned) to which they all celebrate and shout "BOOYAKASHA".
For unknown reasons, Slash and the Mighty Mutanimals ambush Tiger Claw at the docks when he is making a deal with the Fulci Twins to gain the final key ingredient needed for the Mind Control Serum. A fight then breaks out with the Mutanimals easily dispatched of by Tiger Claw, where he's able to capture both Slash and Rockwell whereas Leatherhead and Pigeon Pete were knocked into the water by a car. Claiming they'd be of excellent use to "him" Shredder, Tiger Claw brings the two knocked out mutants back to Shredder's lair. Returning back to the lair with the chemical, Tiger Claw hands it to Baxter Stockman, where he claims he can use it to control the now seemingly feral Karai. However, Shredder wishes to use it on another test subject first, with Slash and Rockwell struggling to break free. Utilizing worms to administer the serum to their brains, the two mutants escape from Shredder's lair with a number of Foot-Bots on their trail before being rescued by the Turtles, Pete, and Leatherhead. Following a return to the lair, both Rockwell and Slash are in terrible shape from the effects earlier with Mikey commenting on them being "off". The serum then takes effect, with Slash attacking Splinter before a fight starting between the two mind-controlled mutants and their allies. Under the influence, Slash and Rockwell easily defeat the remaining Mutanimals and the Turtles before knocking out Raphael and capturing him, with the reason being Shredder desires one of the Turtles for experimentation. Stealing the Party Wagon, the two escape with the others in pursuit aboard the now rebuilt Shellraiser. Following their escape, the two bring Raph to Stockman where Slash holds down the hotheaded Turtle for the worm to administer the serum. After infiltrating Shredder's lair, the Turtles encourage Raph to end Shredder once and for all, completely unaware he's fallen to the serum as well. A massive fight then takes place, where Slash battles Leatherhead, who attempts to reason that they are friends to no avail. Leo is then able to break the control over Raph through mocking him, which Donatello follows up to rescue Rockwell. Blasting him with his psychic helmet, Slash is freed by Rockwell, angering Shredder for the failure of this experiment. The Turtles and Mutanimals then work together to defeat Shredder, but even with outnumbering him 8 to 1, they're all taken down. When Shredder nearly finishes off both Leonardo and Raph, Slash and Leatherhead push one of the statues onto him, which doesn't finish him off after they escape an ambush of multiple Foot-Bots, Tiger Claw, and Stockman. Brought back to the lair, Slash attempts to apologize to Splinter for attacking him because of him being under the influence of the serum and seeing his actions, but being unable to control them at the same time. Splinter understands, stating that Shredder was responsible, not him.
Slash and Rockwell are seen investigating the sewers to find the traces of the Kraang only to run into Zog. After encountering him, Slash and Rockwell are found injured by the turtles and are brought back to the turtles' lair.
After recovering, Slash and the Mutanimals assisted the turtles as well as Mondo Gecko and Muckman in stopping the Triceratons' plan to invade and destroy the Earth using the Heart of Darkness to create a black hole. During the fight, Slash attempted to destroy the machine, but only succeeded in delaying the timer. The Triceratons soon overwhelm them, with Slash among the captured. Later, Splinter and the turtles return with a temporary alliance of Foot Clan to try again to stop the machine. April manages to save Casey from captivity and starts trying to free Slash, but Slash begs April to leave the rest of the captives behind and save herself. In the end, the machine creates the black hole, which tragically devours Slash along with the entire Earth and most of its inhabitants.
Slash appears again with the other Mutanimals (excluding Pete and Muckman), chasing down the Fulci Twins, who are trying to get away with a briefcase. Slash orders Leatherhead to flip their car over, with leads to Rockwell subduing them. Slash opens the briefcase only to find to blueprints he does not recognize. After psychically probing the twins, Rockwell informs the team that they are taking those blueprints to an engineer to build weapons specifically designed to destroy mutants. Shortly after, The Hammer shows up and rendered them immobile with nerve gas that only affects mutants, allowing the twins to escape. At Leatherhead's suggestion, the Mutanimals decided to warn an seek help from the turtles about the huge threat that Don Viziso's gang poses to all mutant-kind. Upon visiting the Turtle Lair, the Mutanimal are greeted and are asked the whereabouts of Pigeon Pete, to which Slash coldly remarks "We don't talk about Pigeon Pete."
Slash was present at Splinter's funeral.
Slash, both unmutated and mutated, shows a great deal of love and loyalty to Raphael. Naturally, since he had been with Raph for years, he silently observed Raph and his family and listened to all of Raph's problems. Once he mutates, he becomes obsessed with removing anything he deems to be holding Raphael back, including the latter's family. Slash is even willing to harm Raph himself to prove that he needs to let go of his more positive qualities so that he may become a "true warrior". Ultimately, while Slash is a crime fighter, he possesses no kindness and seeks to turn Raphael into a relentless killing machine like himself.
However in Newtralized!, Slash was shown to go against killing innocents (and those that assist him) to justify the means, unlike the Newtralizer. He later makes amends with Raphael and helps take down his former partner with the rest of the team. He then leaves on a positive note, preferably to work alone for the time being. In Battle for New York, Slash reveals that his violent and deranged behavior before was due to the effects of the mutagen affecting his psyche and was clearly mournful about his past actions.
In Battle for New York, Part 1 and Part 2, Slash demonstrates leadership skills as the leader of the Mighty Mutanimals. His personality has also stabilized, and he blames the mutagen for causing his unstable behavior in Slash and Destroy. He also regards Leatherhead as a brother, and humbly accepts the alligator's counsel during moments of self-doubt.
- Raphael - Slash's relationship with Raph is complicated, to say the least, as a pet love that turned into a conflicted ambiguous love between two fully-grown sentient mutant turtles. Slash was originally Raph's pet turtle Spike, and one of the only individuals Raph showed love and affection to, Raph usually speaking to him as if to another person rather than to a pet; indeed, Spike's first scene in Rise of the Turtles, Part 2 showed Raph sharing solemn tender words of love to another unseen male character, only for the scene to reveal the recipient to be his non-verbal pet turtle Spike. In the same scene, Raph was deeply embarrassed that Michelangelo witnessed this exchange, implying that Raph prefers not to show tenderness to Spike when others are watching. This kind of tenderness occasionally carried over to Raph and Slash as mutants, as shown in a scene in Clash of the Mutanimals when Raph worriedly rushed to see if Slash was okay. When Spike became the mutant Slash in Slash and Destroy, he demonstrated that he really had been listening to Raph all those years, finally requiting the love Raph had shown him. The two planned to become their own ninja team, but Slash proved unstable, possessive and ax-crazy when he tried to kill Raph's brothers to have Raph all to himself. Raph rejected what Slash had become, and Slash escaped feeling betrayed by the only person he'd ever loved. Raph was so aggrieved by Slash's loss that Splinter had to teach him how to cope with the loss of loved ones. Slash and Raph did not interact much when they met again in Metalhead Rewired, but Slash protected Raph from harm, demonstrating he still cared about him. Raph and Slash finally fully reconciled in Newtralized!, when Slash's stabilizing conscience steadily alienated him from his then-ally, the Newtralizer, and Slash eventually turned against the Newtralizer to defend Raph, his brothers and Casey Jones. Raph invited Slash to come back home, but Slash declined, choosing to remain alone for the time. In The Invasion, Part 1, when the turtles were permanently evacuating the Turtle Lair, Raph revealed his most cherished personal possession to be his photograph of Spike, expressing how much he still worried about Slash. After an exile in North Hampton, Raph and Slash met again in Battle for New York, Part 1, immediately re-establishing their ties. Raph trusted Slash even while his brothers (particularly Leonardo) still doubted him. From this point on, their relationship is more casual, with Raph and Slash appearing as loyal friends but sharing far less affection, except for one scene in Clash of the Mutanimals. Slash is one of the few close friends or family who consistently addresses Raph by his three-syllable name, "Raphael," except for two utterances of "Raph" in Slash and Destroy.
- The Newtralizer - For a time before Newtralized!, Slash thought of the Newtralizer as a brother. This relationship was dissolved after the Newtralizer showed depraved indifference for innocent human life and also tried to kill Raphael and his brothers.
- Leatherhead - Slash met Leatherhead sometime after the events of The Invasion, Part 2, and were founding members of the Mighty Mutanimals along with Dr. Tyler Rockwell, Pigeon Pete and their noncombatant human benefactor Jack J. Kurtzman. In Leatherhead, Slash finally found the brother figure he had longed for, after becoming violently estranged from his previous brother figure the Newtralizer. Slash made Leatherhead his second-in-command of the Mutanimals, placing a great deal of trust in the alligator's counsel.
Friends / Allies
- Casey Jones - In Newtralized!, Slash observed how Raphael seemed to have found a new partner in Casey. Later, Slash would turn against the Newtralizer to protect Casey, Raph and the other turtles from harm.
- Donatello - In Slash and Destroy, the newly mutated Slash tried to kill Donnie along with Raph's other brothers so Slash could have Raph all to himself, and these actions forced Raph to reject what Slash had become. Slash had temporarily collected Donnie's purple mask as a trophy. Though Raph and Slash eventually reconciled in Newtralized!, Slash would not fully reconcile with Raph's brothers until Battle for New York, Part 2.
- Jack J. Kurtzman - Slash's trusted noncombatant human benefactor of the Mighty Mutanimals.
- Leonardo - Slash and Leo were never particularly close, and Slash even tried to kill Leo in Slash and Destroy along with the rest of Raphael's brothers. Leo held a strong distrust for Slash from that time. But in Battle for New York, Slash became the leader of his own team, the Mighty Mutanimals. Raph trusted Slash, but Leo remained distrustful. Finally, Slash admitted that Leo had actually been a role model for him, showing Slash the leadership skills that Slash himself would practice with the Mutanimals. Slash and Leo reconciled at this point.
- Michelangelo - In Rise of the Turtles, Part 2, Mikey walked in on Raphael talking tenderly to Spike, finding it adorable. In Slash and Destroy, the newly mutated Slash tried to kill Mikey along with Raph's other brothers so Slash could have Raph all to himself, and these actions forced Raph to reject what Slash had become. Slash had temporarily collected Mikey's orange mask as a trophy. Though Raph and Slash eventually reconciled in Newtralized!, Slash would not fully reconcile with Raph's brothers until Battle for New York, Part 2.
- Pigeon Pete - Slash's comrade and subordinate in the Mighty Mutanimals.
- Dr. Tyler Rockwell - Slash's comrade and subordinate in the Mighty Mutanimals.
- Splinter - In Turtle Temper, Splinter used Spike as a sounding board to coerce Raphael into listening to the story of his past as Hamato Yoshi and his enmity with Oroku Saki. After Slash's psychotic rampage in Slash and Destroy, Splinter recognized how much Raph loved Slash, and taught him how to cope with the loss of loved ones. Splinter and the mutated Slash had not otherwise been shown interacting prior to Clash of the Mutanimals, which showed them to already be friends; Slash addresses Splinter as "Master Splinter" like the other turtles and April O'Neil do. After Slash and Dr. Tyler Rockwell were reprogrammed as Foot Clan sleeper agents, they were activated when Splinter said the word "water", and Slash savagely attacked Splinter from behind, Slash and Rockwell kidnapped Raphael, stole the Party Wagon and returned to Foot Headquarters. Slash, Rockwell and Raph were deprogrammed and rescued by a combined assault by Leonardo, Donatello, Michelangelo, Leatherhead and Pigeon Pete. Slash humbly apologized to Splinter and begged for his forgiveness, but Splinter held Slash blameless for what happened between them. The severe injuries Slash inflicted on Splinter would last for additional episodes, with Splinter still recovering in The Deadly Venom.
- Foot Clan - The Mighty Mutanimals seemed to start fighting the Shredder's forces almost immediately after the Kraang were no longer a threat. In Clash of the Mutanimals, Slash led a Mutanimal attack against Tiger Claw and the Fulci Twins, but Slash and Dr. Tyler Rockwell were captured, taken prisoner, and the Shredder directed Baxter Stockman to experiment a new mind control technique on them. Slash and Rockwell became the Shredder's sleeper agents. Later, in the Turtle Lair, they were activated upon hearing the word "water", leading them to attack the turtles inside their own lair, kidnap Raphael, steal the Party Wagon and return to Foot Headquarters, where Raph was also reprogrammed. Slash, Rockwell and Raph were deprogrammed and rescued by a combined assault of Leonardo, Donatello, Michelangelo, Leatherhead and Pigeon Pete on the Foot HQ.
- The Kraang - Slash's enmity with the Kraang began sometime before Metalhead Rewired, when the Kraang captured him along with various other mutants. With the Newtralizer's help, he finally escaped Kraang captivity, and made a pact with the Newtralizer to completely destroy the Kraang. This alliance disintegrated in Newtralized!, but Slash continued to oppose the Kraang, eventually uniting with Jack J. Kurtzman, Leatherhead, Dr. Tyler Rockwell and Pigeon Pete to form the Mighty Mutanimals and fight the Kraang together. This team cooperated with the turtles in Battle for New York, Part 1 and Part 2 to finally wrest control of New York City from the Kraang.
- The Newtralizer - Slash and the Newtralizer met each other when they were both prisoners of the Kraang, as revealed in a flashback scene in Newtralized!. They helped each other escape, and immediately became allies, swearing to destroy the Kraang together. Slash had also been feeling betrayed by Raphael's rejection in Slash and Destroy, and Slash latched onto the Newtralizer as a brother figure. As Slash's conscience stabilized, he gradually realized that he valued innocent human life while the Newtralizer did not. Soon after Slash met Raph again, Slash's relationship with the Newtralizer rapidly disintegrated, and Slash finally turned against the Newtralizer to protect Raph, his brothers and Casey Jones. The Newtralizer escaped, now an enemy of Slash. Slash's experiences with both Raph and the Newtralizer would echo in his future relationship with Leatherhead, the brother figure he always wanted and finally found (aside from Raph).
Spike could not speak and had no dialogue of his own.
Raphael: I know you're a little worried about me. Look, I'm not gonna lie to you. We've never gone into a fight like this, and...I don't know what's gonna happen. But you don't have to worry. I will make it back.
Raphael: Who does Leo think he is?! So what if I got a temper? I'm still the best fighter we've got. In fact, if anything, my anger makes me a better fighter. You understand me, don't you, Spike? Chew on your leaf if you understand me.
Raphael: Oh look, Spike. Donnie got another stick to break.
(Leonardo is watching Space Heroes, but Raphael hits the television's power button with his shuriken.)
(The turtles return to their lair.)
(Projects from an explosion from Donatello's lab is destroying random objects in the living room.)
Donatello: We gotta move. Everyone gather one meaningful thing you wanna take with you. First we find Splinter, then we get out of town.
Raphael: Always me, right? I've got the bad attitude. I'm the bad guy. They just don't get it.
Raphael: I can't believe this is happening. This is amazing! Wait. What am I gonna tell the others?
(Slash puts on his black mask.)
Slash: If Raph's gonna be free, we may need to lose some dead weight.
Raphael: Yes, this is so cool! Just you and me! Raph and Slash! The crime-fighting duo!
Slash: Raphael. You said it yourself. We don't need these clowns. We gotta hunt that mutagen down, now.
Leonardo's voice: Mikey! Mikey! Down here! I need your help!
Slash: I spent years watching ya train. Learning your moves. I know everything you can do.
Slash: Ha! It's over, Raphael. You've lost.
Slash: A true warrior's spirit. Haha, we're the same, you and me.
Leonardo: So what's with the new turtle?
Heh, heh, heh. My turn.
Keep me prisoner? HAAAAAAAH!
I'm gonna rip, every tentacle off ya!
It's Slash now, remember? Good to see you again Raphael, miss me?
We're taking care of the Kraang. I got a new partner now.
What you Turtles couldn't, whipping out the Kraang. Keep out of the way!!!
Blow this place? Too dangerous. What about the humans out on the street?
I owe you one. The name's Slash.
I'm with you brother. Destroy the Kraang at any cost.
Eager for another beatdown Donatello?!
...I'm here to take out Kraang, not people!
And I'm suppose to trust you inside that thing?!
You're no brother of mine!
I need to go my own way Raphael. Think I'm better off solo.
Goodbye brother. I'll see you all again, someday...
Meet my team... The Mighty Mutanimals!
- Slash is voiced by Corey Feldman, who previously voiced Donatello in Teenage Mutant Ninja Turtles (film) and Teenage Mutant Ninja Turtles III. Feldman also co-starred with Sean Astin (who voices Raphael) in the 1985 movie The Goonies.
- Slash's belt buckle is actually a hood ornament from an old car.
- Slash can impersonate Leonardo.
- Slash is one of the hardest enemies to defeat, mainly because of his super strength and knowledge of all of Raphael's moves.
- Slash is a ruthless fighter, but has a sense of honor in that he will not harm innocents and civilians.
- In Slash's concept art, his skin color is the same as that of the 1980s action figure version of Slash. In the TV series, the color of Slash's skin varies significantly without explanation, even during the same episode, ranging anywhere between dark spring green and Prussian blue. The unmutated Spike was olive colored.
- After his mutation, Slash resembles an Alligator-snapping turtle.
- Since mutating, Slash has changed appearance in subtle ways. In Newtralized!, he lost a large chip off the top-right-most spike of his carapace, which Leonardo used to identify his involvement. This spike had fully grown back by Battle for New York, Part 1, but Slash had a new change in appearance—his lower jaw very noticeably yellowed for unknown reasons.
- Slash's spiky carapace strongly resembles an extreme form of a turtle health condition called pyramiding, which is when the scutes (individual segments) of the carapace grow outward in pyramid-shaped spikes. In real turtles, this is a form of metabolic bone disorder thought to be caused by inadequate humidity or improper diet, and is found almost entirely in pet land turtles. Though owners often consider pyramiding attractive and exotic, it actually means the turtle has potentially serious health problems; these problems are treatable, but the pyramiding itself is irreversible and adds certain difficulties to a turtle's life. Healthy turtles without this condition have smooth round shells, just like Spike before his mutation.
- If Slash's massive carapace spikes are solid and rigid, they would appear to pose a physical obstacle if he were to try to lie on his back or sit with his back against an object. But in Battle for New York, Part 2, in the scene where the Mighty Mutanimals are being held inside a transparent jar holding cell at TCRI, Slash sits down against the transparent wall, and his carapace spikes seem to disappear where they intersect with the wall's surface.
- Slash is similar to Mirage Splinter in that he wasn't specifically trained in ninjutsu, but learned ninjutsu by observing ninjas in training. Whereas that Splinter observed his human owner Hamato Yoshi, Spike observed Raphael, his brothers and Splinter. Mirage Splinter regarded Hamato Yoshi as his master, and 2012 Slash regarded Splinter as "Master Splinter".
- The interior of the symbol on Slash's belt buckle is identical in appearance to Deathstroke's symbol, which he puts on his equipment and apprentice suits in the Teen Titans TV series.