Futurama S02 E09 Why Must I Be a Crustacean in Love?

"Defying gravity and common sense."

When Dr. Zoidberg runs amok during the Decapodian mating season, Fry sets out to teach him how to woo a mate. Things backfire when Zoidberg's desired mate falls for Fry instead, and Zoidberg challenges Fry to a battle to the death.