TMNT (1987) - S01E02: Enter The Shredder

Foot Clan leader Oroku Saki, the Shredder decides, along with his partner Krang from Dimension X to turn two thugs into mutant henchmen using the mutagen that created Splinter and the turtles. Thus Bebop turns into a warthog and Rocksteady turns into a rhino. The Foot Soldiers kidnap Splinter, and the Turtles go rescue him at the Technodrome.