Teenage Mutant Ninja Turtles return to Nickelodeon Oct. 12 in a two-part premiere that will lay out the course for the entire second season of the hit animated series.

In "The Mutation Situation," the Turtles discover the alien Kraang survived their previous encounter and have dropped mutagen canisters across New York City. Throughout the season, the Turtles' mission is to recover those canisters before more mutants can be created -- all while the Kraang and Shredder unite to put an end to Leonardo, Raphael, Donatello and Michelangelo.

The new season also sees the addition of Nickelodeon veteran Josh Peck (Drake & Josh) as the voice of fan-favorite Casey Jones, a teenage hockey player who'll team with the Turtles and help them try to unravel the mystery of why April O'Neil is so important to the Kraang.

Teenage Mutant Ninja Turtles returns Saturday, Oct. 12 at 11 a.m. ET/PT on Nickelodeon.