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:
- Badass Boast: "The Foot shall rise again like a tidal wave and come crashing down on, crushing the life out of you by these hands!"
- Batman Gambit: Certain the Turtles wouldn't be gone forever, Khan got his hooks in Casey to learn all about them and have an immediate way to be alerted to their return.
- Bear Hug: Casey when he sees the Turtles are back.
- Big Damn Reunion: April and Casey are thrilled and relieved to see Turtles returned.
- Big "WHAT?!": Khan when Mikey drives the Turtle Hauler through the wall of his dojo.
- 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: Khan is seen running a martial arts school, whose students include Casey.
- Explain, Explain... Oh, Crap!: When laying eyes on Khan.Mikey: Haven't we seen this guy before somewhere?
Raph: Yeah, wasn't he the bozo from—?
Leo: The future with the three Shredders. - Fighting Your Friend/ Let's You and Him Fight: Khan brainwashes Casey and makes him fight the Turtles, much to their despair.
- Group Hug: How Leo, Raph, and Mikey greet April.
- History Repeats: Don blames himself for his failure and stars behaving like a jerk to his brothers and starts being too obsessed with his work, similar to how Leo did in the fourth season.
- "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.
- Nice Job Breaking It, Hero: Khan boasts that he can anticipate the Turtles' moves because he got Casey to tell him about their moves and abilities.
- Not Quite Dead: The final scene in the lair reveals Splinter is still alive.
- O.O.C. Is Serious Business: Donatello gets snippy with all this chatter, while he's trying to work. Mikey says he's more of a grump than Raph.
- Preemptive Apology: Leo apologizes to a brainwashed Casey before he and Raph take Casey down.
- Properly Paranoid: April thinks Casey has been acting unusually ever since he started studying under Khan.
- Tactical Withdrawal: Khan proves to be too much of a handful even for three Turtles, so Mikey gets the Turtle Hauler for an escape. However, so it's not a total loss, he takes the opportunity to inflict enough damage to cause the building to collapse.
- Temporarily a Villain: Casey, while under Khan's control.
- Time Skip: A year has passed for April and Casey since the Turtles disappeared.
- 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.
- Unwitting Pawn: Khan milked Casey for information about the Turtles and kept him on as a way to be alerted to their return.
- Villain with Good Publicity: As far as Casey knows, Khan is a great and honorable man.
- Wham Shot: How we learn that Casey's vaunted teacher is the guy who faced the Turtles in last episode's Bad Future.
