S05E06: Less Than Hero

Suffering from aches and pains, Fry and Leela turn to Dr. Zoidberg who gives them a "miracle cream" that he bought long ago from a traveling salesman. Lo and behold, when they try it out, it actually is a miracle cream that gives them superpowers. Fry and Leela decide to become super heroes with Bender as the third member of their team.