Rupert is a Alien Turtle salesman from the Planet of the Turtles. Shredder stole a Personal Energy Projector an invention he was selling on TV. Shredder got followed by Rupert and the Flying Turtlenecker Brothers back through the portal to Dimension X as he was stealing the projector.
He was taken prisoner abound the Technodrome along with the Ninja Turtles. However Splinter and April O'Neil rescue them and they split up. Donatello and Rupert go to the Planet of the Turtles to look for Dr. Turtlestein, the inventor of the projector, to see if he knows of a way to stop it. Donatello, Dr. Turtlestein, and Rupert come back just in time with a Portable Portal and Donatello reverses the effects of the projector, sending the energy back to Earth. Dr. Turtlestein uses the transporter to send the Turtles, back to Earth.