Bender searches the universe for his missing body parts after an alien street gang has him stripped down to his bulb eyes and mouth grille.
As he's being taken to jail, Yuri agrees to give up a list of buyers for Bender's parts and a giant robot head for URL in exchange for his freedom.
His antenna (or "Robo-dong") is traced to The Beast With Two Bucks Sex Shoppe, where with the aid of a photo taken by a secret toilet camera they discover it was sold to Hedonismbot.
His chest is found in the ERR frat house at Mars University where it's being used as a beer keg and his legs are recovered from a hospital where they had recently been transplanted to Tinny Tim.
Tarquin, Fry and Leela persuade Bender to leave the ass behind in the lighthouse in order to save the lives of sailors and their legacy of swearing.
It manages to save a child named Johnny who has fallen down a gravity well on his space farm and returns to a grieving Bender at Planet Express amid a flourish of fireworks in the sky which, on inspection, actually turn out to be the spectacular crashes of several ships in the murky Sargaseous Sea.
[1] Max Nicholson of IGN gave the episode a 7.5/10 "Good" rating, saying "Bender's ass took center stage in this week's Futurama, and it actually kinda worked.