While Shredder and Krang are struggling to fix their transdimensional portal, Donatello reveals that he has been working on a portal of his own. They accidentally bring Usagi Yojimbo — a rabbit ronin from an alternate Earth where anthropomorphic animals thrive — to New York.
Tropes:
- Aliens Speaking English: Raphael lampshades the absurdity of a Japanese rabbit from an alternate universe speaking American English.
- Bittersweet Ending: The turtles manage to save the dragon from being killed and things are back to normal, but Usagi is still stranded in New York and Donatello is the only one who can do anything about it.
- Fighting Clown: Splinter refers to their style of fighting Usagi "Slapstick".
- Rōnin: Usagi identifies as one.
- Trapped in Another World: Donatello's prototype trans-dimensional portal winds up opening a portal that spits Usagi from his dimension into theirs.
- Weapons Breaking Weapons: Usagi cut Leonardo's swords with his 300-year-old blades, and diced up Donatello's staff. Neither of which he's done in his home universe.
- World of Funny Animals: Usagi's dimension is a world of anthropomorphic animals in Feudal Japan.
