During the mission to free the mutated populace of New York from Dimension X, Slash returns leading his own band of mutants.
Tropes:
- Achievements in Ignorance: Mikey was just playing Mad Scientist with Donatello's lab kit and accidentally created retromutagen. Not only that, the new batch can even turn regular mutagen into retro-mutagen! Just don't ask him to make more, considering he was just throwing random things in a beaker.
- Attack Its Weak Point: The Kraathagatrons' weak point is shown to be their "butt-faces"; Mikey drives one away by throwing an explosive crystal at that spot.
- Borrowed Catchphrase: Mikey jokingly recites a list of Leo's "Leo-isms" prior to their thoroughly insane plan to save the enslaved Human-Kraang hybrids in Dimension X.
- The Bus Came Back: Slash, Leatherhead, Pigeon Pete, Dr. Rockwell, Kurtzman, and surprisingly Kraang Sub-Prime (along with his Irma disguise) all make their return, as do the Kraathagatrons and Kraang apes.
- Canon Immigrant: Not the characters themselves, but the Mighty Mutanimals first appeared in the comics.
- Continuity Nod: Slash and Leo carry a lot of tension; Slash from the resentment he built up listening to Raph's one-sided stories about Leo for years, and Leo for the brutal beat down Slash gave the Turtles when he debuted.
- Michelangelo brings back his "Savage Mikey" look from "Into Dimension X".
- Crazy Enough to Work: Mikey and Donnie's plan to hijack a Technodrome in order to convert the mutagen contained within to retro-mutagen in order to revert the enslaved Human-Kraang hybrids to humans.Raphael: This is so crazy, I'm startin' to like this plan.
- Get a Hold of Yourself, Man!: Rockwell to Pigeon Pete in Part 2.
- Guns Akimbo: Mikey dual-wielding Kraang laser rifles while flying about on a pair of Kraang hoverpods.
- Rockwell doing the same with his mind.
- Hypocrite: Leo calls out Slash for using the other Mutanimals as bait even though he's done the same thing with Mikey several times and another time with Raph.
- I Know Mortal Kombat: Mikey's justification:Mikey: Dimension X plus years of video games equals Mikey awesomeness!
- Lampshade Hanging: Kraang Sub-Prime does this on the Kraang voices, along with the fact that the invasion of New York has taken forever.
- Mythology Gag: The Mighty Mutanimals first appeared as a spinoff of the Teenage Mutant Ninja Turtles Adventures, featuring an almost entirely different roster (Leatherhead is the only member common to both versions). This marks their first television appearance.
- Donnie calls the Kraang teleporter a "transmat device", a term taken from the Mirage comics and 2003 series.
- Upon their triumphant return from Dimension X, Mikey starts singing the "Ninja Rap."
- Offscreen Villain Dark Matter: Averted. The reason the Kraang invasion has not spread to the rest of the world is because their massive invasion of New York that involved mutating millions of people cost them the majority of their mutagen supply, thus averting Easy Logistics.
- Only Sane Man: When the turtles and the Mighty Mutanimals first meet, 3/4th of both teams end up objecting to teaming up and arguing with each other. Only Mikey and Leatherhead stay calm and understand their teams need to work together. It of course helps that the two of them are already friends.
- Out of Focus: Splinter, April , and Casey are left to take care of Kurtzman, and the next episode reveals Casey's not happy about being left out of the action.
- Series Continuity Error: What was that about time moving much faster in Dimension X?
- Shout-Out: Slash calls a Kraang ape a "darn dirty ape"!
- Kraang Sub Prime shouts "Here's Kraangy" while trying to get to the turtles
- Donnie seems to be channeling Scotty when the Technodrome they're piloting malfunctions.
Donatello: The engines just can't take retro-mutagen, Captain! - Suddenly Voiced: Dr. Rockwell speaks for the first time, as a result of Kraang experimentation on him, and having regained his intellect.
- Sesquipedalian Loquaciousness: And now that he can talk, he seems intent on flaunting his vocabulary at every opportunity.
Rockwell: We are in a staggeringly phenomenal amount of danger. - Surrounded by Idiots: Kraang Sub Prime feels this way with the generic Kraangs still speaking broken English.
- The Team Benefactor: Kurtzman - the behind the scenes adult commander like Splinter.
- Took a Level in Badass: The first time we saw him, Pete didn't seem to have any combat potential, but he quickly fixes that in this episode.
- While Dr. Rockwell wasn't that much of a wimp before, now he's regained his intelligence along with developing various psychic powers, including telekinesis and mind control.
- Took a Level in Jerkass: Rockwell becomes a near borderline Insufferable Genius towards Donatello.
- Took a Level in Kindness: Leatherhead's anger doesn't seem to make him a threat to his allies anymore.
- Unexplained Recovery: After being crushed during the second season finale, Kraang Sub-Prime makes a comeback, and it's not explained how he survived none the worse for wear. He is seemingly Killed Off for Real after a Kraang Stealth Ship he is on crashes into a Technodrome and explodes.
- Ungrateful Bastard: Lampshaded by Leonardo after the couple he saves call him an alien turtle and run away.
- Unusual Euphemism: One of the Kraang in response to the Mutanimals breaking into TCRI.Kraang: Oh, Kraang.
- Raphael says the same thing when he and his brothers are surrounded by Kraang droids in Dimension X.
- What Happened to the Mouse?: Kraang Prime is nowhere to be seen.
- In terms of items, Slash's plutonium teleporter from Newtralized is never seen.
- You Are Better Than You Think You Are: After the Mutanimals are captured by the Kraang, Slash starts to doubt whether he's fit to be a leader. Leatherhead thinks otherwise:Leatherhead: I have seen you save humans from the Kraang, rescue your fellow mutants. You are a good soul, Slash.
