Teenage Mutant Ninja Turtles: Turtles at the Earth's Core (1991)

Shredder and Krang discover a Dinosaur reserve at the earth's core and plot to steal their life source, an energy crystal, to repower the Technodrome, drill to the surface, and comence w/ world domina.. blah blah yada yada and of course the turtles are ready to stop 'em. In the next episode the Ratking makes his debut and plots to control Splinter and make him a part of his rat army.