Episode 49 of "Futurama"
s04e05 Leela's Homeworld

After Bender dumps toxic waste into the sewers, the mutants become angry and kidnap Bender, Fry and Leela. They suspend the crew over a radioactive lake and threaten to dump them in, altering their human genes and mutating them, but two hooded mutants save them. Leela decides to pursue the mysterious mutants, who seem to have a suspicious fixation with her.