The Butterjunk Effect

The Planet Express crew are assigned to return the "stolen" Moon rocks from the Apollo missions to the Moon. There, they attend a "Butterfly Derby" where women in butterfly wingsuits battle and wrestle each other to near-death. When the announcer Abner Doubledeal asks for amateur challengers to the current reigning champions, Leela and Amy step forward. They are severely trounced by their opponents on their first attempt but are nonetheless offered opportunities to become a regular Butterfly Derby team called the "Wingnuts". The pair are unable to improve on their first performance and lose every match they're placed in. While in the locker room, they see the champions buying a substance called "Nectar" that helps them to build body strength. Leela and Amy quickly jump at the opportunity and buy Nectar themselves, soon becoming as strong as the champions and developing a long winning streak in further matches. Meanwhile, Fry and Kif have found their respective girlfriends, Leela and Amy, to be brutish, unromantic and abusive while on the influence of Nectar.

Soon, their Nectar supplier runs out when the reigning champions buy out the remaining supply. The Professor realizes that Nectar is a substance created by a flower on Kif's home planet, Amphibios 9, and Kif, Fry, Bender, Leela, and Amy set off to collect more. At a butterfly preserve on Kif's home planet, they are told to beware the male butterflies by the Grand Butterfly Curator. Fry discovers the insect first, who sprays Fry with copious amounts of liquid in self-defense. Having collected enough of the nectar, they spend the night at Kif's parents' home, each sleeping in separate bedrooms. Leela becomes uncharacteristically enamored with Fry, but both are shocked when Amy becomes just as aroused by him. On return to Earth, they realize that the liquid contains the male butterfly's mating pheremones. Amy and Leela's abuse of Nectar has made them susceptible to the butterflies' pheremones and they are forced to quit Nectar cold turkey in order to break its hold on them. During this time, Fry begins to feel weird, and at one point, creates and envelops himself in a cocoon aboard the Planet Express ship.

After overcoming their addiction, Leela and Amy have one more match in the Butterfly Derby against the reigning champs. To add to the excitement, the match is held over a pit of lava. Without the Nectar, Leela and Amy are quickly outmatched, the champions tearing their wings and forcing them to fly together to avoid falling into the lava. As the champs attempt to tear off the last of their wings, Fry awakens from the cocoon as a large butterfly and enters the arena. The champions are drawn to his pheremones, allowing Leela and Amy to leave the arena safely. After the match, the Planet Express crew recovers Fry believing him to have fully transformed into an insect by the liquid. But soon, the insect shell cracks open revealing a delirious and still human Fry inside.

Zack Handlen of The A.V. Club gave the episode a "B-", describing it as, "passable, but not particularly inspiring."[2]

• "The Butterjunk Effect" at IMDb
• "The Butterjunk Effect" at TV.com
• "The Butterjunk Effect" at the Infosphere, the Futurama Wiki