"It tastes like there's a party in my mouth...and everybody's throwing up."
Parasites Lost is the second episode of the third production season, and fourth episode of the third broadcast season of Futurama. It originally aired in North American on May 20, 2001.
The Planet Express crew stops at Greasy Sue's Greasy Truck Stop to refuel the ship with dark matter. Fry, while waiting, eats an egg sandwich he bought for 25c out of the truck stop restroom. Sal and other truckers
at the truck stop start hooting and cat calling at Leela to Fry's dismay. He tries to defend her honor, but manages to insult her more.
Back at Planet Express, Fry and Bender "fix" the plasma fusion boiler, causing an explosion. A lead pipe is stuck in Fry's chest, leading Zoidberg to discover that Fry is infected with worms after they remove the pipe and heal the hole from the inside. Farnsworth decides that they'll have to go deep inside Fry to remove the worms using his latest invention, Micro-Droid Machines. Since Fry can't know about the mission as the worms would find out and try to stop them, Leela is appointed to keep Fry distracted.
Leela shoots the crew into Fry's ear with a mouth dart. She takes him on a walk as the crew flies deeper into Fry, past worms repairing parts of his body and even improving upon them, leading to a stronger and smarter Fry. While on their date, Fry shows off his new muscles and intelligence, impressing Leela. Fry beats up Sal, making him apologize to Leela. The crew, having reached The Stately Capital of Fry's Bowel, tries to attack the worms, but they fight back.
Fry tells Leela that he loves her, but Leela, realizing that the new Fry is being influenced by the worms and, liking this new him, uses a micro-droid to stop the crew from getting rid of them. Fry thanks Leela for saving the worms and they start dating. Leela takes Fry back to her apartment where he plays the holophoner for her. When Leela tells him she loves what he's become, Fry worries that she loves him for the worms and not himself.
Fry shrinks himself and meets with the Mayor of Colon and asks the worms to leave. The worms refuse, leading to a cinematic sword fight. They end up in the brain, where Fry threatens to cuts his own medulla oblongata unless they leave. The worms, in a panic, leave Fry's body.
Fry returns to Leela's apartment to play the holophoner for her again. Leela is shocked to discover that she was in love with Fry's worms and kicks him out. Fry tells Bender that Leela is a lost cause, but he secretly practices the holophoner, conjuring up a crude image of Leela.
Two signs read "Human Milk" and "Watch for Falling Humans" in Alienese.