When a battle between the Purple Dragons and what appear to be the Teenage Mutant Ninja Turtles is captured on film, the Turtles are quick to refute their master Splinter's accusations of carelessness. Breaking into the Purple Dragons' headquarters to get to the bottom of these mysterious doppelgangers, our Turtles discover that their "imposters" are, in fact, versions of them from another dimension. The goofy other dimensional "1987 Turtles" prove to be a hassle for the more serious-minded "2003 Turtles", but they are soon able to discern that they were teleported into their world in a dimensional portal accident that has also brought their arch-enemies, the Shredder and Krang, and their battle fortress, the Technodrome, along with them. The eight Turtles head below the ground to track down the Technodrome, but their presence together only clues the Shredder in to the fact that there may be a version of himself on this world that he can ally with to take the Turtles down.