The Turtles reunite with Casey and April, who are overjoyed to have their friends back after a year apart. During his friends' time in the future Casey joined a martial arts school, but when the Turtles investigate it they find some old enemies behind the scenes.
This episode provides examples of
- Brainwashed and Crazy: All of Khan's students
- Deadly Dodging: Mikey, Raph and Leo do this to defeat Khan's brainwashed students, since they don't want to hurt them
- Evil Mentor: Khaan is seen running a martial arts school, whose students include Casey.
- Fighting Your Friend/ Let's You and Him Fight: Khan brainwashes Casey and makes him fight the Turtles, much to their despair
- "I Know You're in There Somewhere" Fight: Raph and Mikey initially try this on Casey, before Leo points out that it won't work
- Preemptive Apology: Leo apologizes to a brainwashed Casey before he and Raph take Casey down
- Temporarily A Villain: Casey, while under Khan's control
- Took a Level in Badass: Casey undergoes a bit of this when training under Master Khan (he manages to sneak attack and take down all four of the Turtles in this episode) but brainwashing is involved and the show doesn't give any strong indication of whether he retained his new found fighting skills afterwards.