Shape-shifting alien is a criminal from the year 2105. He appears at the Galactic X-Treme hoverboard tournament in New York, where he plots to kidnap Cody Jones.
The Shape-shifting alien (no name given) observes Zip Zemo conversing with Cody and realizing they are friends, takes on Zip's form in order to get close to the boy. When Cody is temporarily separated from the Turtles, the shape-shifter uses the opportunity to lure Cody away. Realizing that Cody is no longer with them, Raphael turns around and sees him talking to Zemo, but then he and Mikey also see Zemo on the live TV feed. The shape-shifting imposter grabs Cody, and Michelangelo and Raphael chase them into the hoverboard arena.
When the imposter snatches up a hoverboard, the two Turtles grab a pair for themselves. Meanwhile, Leo and Don, laden down with snacks, are in their seats wondering where the others have gotten to. Don looks up and spots the imposter Zemo on a hoverboard, with Cody slung over his shoulder. Seeing that he's being followed, the shape-shifter tosses a pair of grenade pellets and manages to knock Michelangelo off of his hoverboard. He then starts firing a laser gun at Raphael and blows out the end of his hoverboard. Raphael leaps off the flaming board and takes another hoverboard from a nearby rider so that he can continue the chase.
Determined to end the chase, Raphael throws his sai at the imposter, snagging both his shorts and the hoverboard. Out of control, the imposter slams face first into a nearby building and the real Karbon Zemo zips under the falling Cody and catches him. Aloysius Biggles takes the shape-shifting alien, now back in his original form, into custody.
During the chase scene, the shape-shifter references a "boss" who is waiting for Cody to be delivered. This mysterious boss remains unknown.