The Turtles go up against the Kraang as they're delivering a shipment of Mutagen. In the process, disaster strikes and the two parties gain another enemy neither of them wanted to have.
Tropes:
- Aesop Amnesia: For the third time, the Turtles forget not to be cocky or arrogant. To their credit, they stop their behavior fairly quickly.
- This is Justified Trope as they're teenagers and it usually takes a teen a few times to really understand life lessons. The fact that they stopped the behavior rather quickly probably means the lesson is finally starting to sink in.
- Brutal Honesty: Mikey straight-up told April that it was their fault for her father's mutation.
- Butt Cannon: The Biotroid has two of them, much to Donnie's shock.
- Continuity Nod: Aside from a new rocket, the turtle gliders, Kraang orb and April's war fan all make reappearances.
- Downer Ending: Mutagen canisters are all over New York, April's father has become a monster because of it, and since the spilled mutagen was because of the Turtles' blunder, April no longer wants anything to do with them.
- Easily Condemned: Right after Mikey confesses the Turtles' part in mutating Kirby, April is quick to believe they did it on purpose and severs ties with them, leaving Donnie heartbroken.
- Evolving Credits: First episode to feature the opening being reworked, which was updated to include the most up-to-date Rogues (Rat King, Snakeweed, Mrs. Campbell, Kraang Prime, among others), as well as some other characters.
- Innocently Insensitive: Mikey, seriously. The way he tells April that they were the ones who spilled the mutagen on Kirby just makes you want to punch him in the face.
- It's All My Fault: April blames herself for her father's mutation until Mikey lets slip that it was actually the Turtles' fault.
- Never Trust a Trailer: Not many trailers put emphasis on the conflict in the later half of the episode (Kirby's mutation), instead focusing on the first half and the monster the Kraang use.
- Nice Job Breaking It, Hero: The Turtles accidentally mutate Kirby O' Neil.
- Mikey basically ruins the Turtles' friendship with April when he reveals it was their fault.
- Oh, Crap!: "Butt cannons? IT HAS BUTT CANNONS!?!?"
- Organic Technology: The Biotroid.
- Poor Communication Kills: Mikey confesses to April that they, the Turtles, spilled the Mutagen on Kirby, but because he only mentioned it was their fault, April jumped to the conclusion they did it on purpose and cuts all ties with them.
- Senseless Sacrifice: Kirby could have gotten both April and himself out of the way instead of just shielding April with his own body, but he may have panicked and wasn't thinking straight.
- It turns out later on that April is immune to mutagen, like she is to Kraang water, another reason why his sacrifice was pointless. note
- Shout-Out: To "Dramatic Chipmunk" in the Sequel Hook.
- Spin Attack
- Thrown Out the Airlock: A rare nondeadly accidental example but still pretty bad since it was due to this airlock that dozens of canisters of ooze fell out (with one landing on poor Kirby).
- We Used to Be Friends: April cuts off all ties with the Turtles when she finds out about her father's mutation, breaking poor Donnie's heart in the process.
- Wham Episode: Kirby is now a mutant and April hates the Turtles because it's their fault, making it clear that she doesn't want to see them again.
- What the Hell, Hero?: In-Universe. April has this episode when she found out it was the boys' fault for her father's mutation (but it was an accident).
- A meta example would be the fans' reaction when it seemed Leo, Raph, and Donnie weren't going to tell April it was their fault that her father mutated.
- Though to be fair, they might not have done it so bluntly like Mikey unintentionally did (he did say it in a sense that kinda made it seem like they did it on purpose). note
- A meta example would be the fans' reaction when it seemed Leo, Raph, and Donnie weren't going to tell April it was their fault that her father mutated.
