When Nibbler falls ill from worms that threaten to take away his intelligence, the crew shrinks down and explores Nibbler's sandbox.
Tropes in this episode:
- But for Me, It Was Tuesday: The worms don't remember being in Fry's body, with the head worm saying "I'll take your word for it" when told by Fry. Possibly a subversion, as "Parasites Lost" implied the worms have a short lifecycle, considering the head worm in that episode stated "I was born here, I raised a cloud of children here, my ancestors came over here on the sandwich". So these aren't necessarily the exact same worms, but they could be their descendants.
- Continuity Nod: Leela and Nibbler watch "Quizblorg, Quizblorg" at the movies.
- Dogs Are Dumb: Discussed about terriers at least. It's been stated by a vet that the parasites will make Nibbler so dumb that his intelligence will be comparable to that of a terrier in the end.
- Incredible Shrinking Man: The crew are shrunk down to fight the worms in Nibbler's sandbox.
- Lamprey Mouth: The Sand Worm has several rows of rings of fangs. It turns out the "fangs" are actually swords held by the worms making up the creature.
- Mix-and-Match Critters: One of the lifeforms in Nibbler's sandbox is described as a "Pygmy-Hyena-Mole".
- Mushroom Samba: Zoidberg has a brief one after consuming the glitter in the sandbox, imagining the others distort and bright colors.
- NOT!: Done by Fry when he tricks a worm into tying himself into a knot by dodging his blasts.Fry: Nice dodging...knot!
- O.O.C. Is Serious Business: Leela, an environmentalist and Animal Lover, convinces everyone to kill all the mites that are infecting the worms because she is desperate to save Nibbler. When Fry calls her out on this, she says they've got to draw the line somewhere.
- Out-of-Character Alert: The worms threatening to decrease Nibbler's intelligence turn out to be the same ones that once inhabited Fry's body. Leela realizes something's up because they increased Fry's intelligence that time, and sure enough, it turns out the worms themselves are infested with tiny mites sucking on their blood.
- Paste Eater: Fry as a kid to the point where his mom would hide his medicine in it.Farnsworth: That's sad and dumb!
- Phlebotinum-Induced Stupidity: The main effect of the worms this episode is that they eventually reduce Nibbler's intelligence to that of a terrier. It eventually turns out that this shouldn't happen, only occurring because the worms themselves are suffering from parasites.
- Pretentious Pronunciation: The dung beetles insist on pronouncing dung with a long U sound and an "almost silent" G, to drive home the reference to Dune.
- Pun: Bender remarks he has a grandfather named Pounder and subsequently remarks that he must be a "quarter Pounder".
- Sandworm: One of the creatures which live in Nibbler's sandbox is a giant sandworm. When the crew encounters it a second time, it turns out to be The Worm That Walks, composed of the worms which once inhabited Fry's body.
- Sequel Episode: To "Parasites Lost", focusing on the return of the parasites which were once in Fry's body.
- Series Continuity Error: It's a necessary plot point here that Nibbler cannot poop outside of his litterbox and therefore cannot avoid reinfection by the worms, except he did just that in "The Why Of Fry".
- Shout-Out:
- The whole episode references Dune, including the Dung Beetle insisting their name be pronounced as "Dune Beetles", a sand world, the glitter being akin to Melange, and a Sandworm.
- Nibbler has a Bart Simpson chew toy.
- In response to his slipper being chewed on, Farnsworth has Nibbler wear "the cone of shame".
- Spoiler Title: When the crew finally track down the worms infesting Nibbler three-quarters of the way through the episode, they discover they're the same worms that infected Fry in "Parasites Lost." This is unlikely to surprise the audience due to the Cross-Referenced Titles.
- Take That!:
- Nibber requesting American cheese (as opposed to gouda or brie as earlier) is treated as a sign that he is losing his intelligence.
- When Nibbler mentions he's close to losing his intelligence, he says his intelligence has lowered to the point where he can no longer predict the end of a M. Night Shyamalan movie.
- Tastes Like Purple: Bender claims he interprets singing as smells, and Fry's singing smells really bad.
- To Serve Man: Nibbler eats a person who was intending to sue after he ate his dog beforehand.
- The Worm That Walks: The Sandworm spotted in Nibbler's sandbox turns out to be composed of the parasites in Fry's body, acting as a single cohesive unit.
- Trojan Veggies: According to Fry, his mum always used to hide his medicine in something yummy, like paste. Farnsworth calls it "sad and dumb" and suggests putting Nibbler's medicine in a block of cheese (namely brie since it's Nibbler's favorite), which works.
