Donatello decides to create a clone of himself so that he can spend more time on his inventions while his clone spends more time fixing things around the Lair. Donny tests his latest invention on a sewer rat and accidentally gets his hand in the way, causing the rat clone to talk just like Donatello. The talking rat is discovered by The Rat King and is convinced by a local hood, Pinky McFingers, that they could take over the world with Donatello's invention.