But whereas the worms’ original appearance ended with Fry destroying them for his own self-gain, “Parasites Regained” ends with the gang reconciling with the worms. Thanks to a bunch of spice-induced hallucinations that “Dune” fans are already familiar with, Leela manages to the figure out the real reason the worms are making Nibbler dumber: They themselves are infected by parasitic worms. Leela remarks that this is “too many layers” to the circle of life, urging the worms to kill off their mites instead of trying to peacefully co-exist with them.
It’s a dark yet strangely heartwarming ending in that way only “Futurama” can pull off. Yes, it involves thousands of mites being killed off mere minutes after Nibbler waxes poetic about the value of all lifeforms no matter how small, but it also means Leela gets to enjoy her loving relationship with her adorable pet Nibbler once again. It also serves as closure to any fan who might’ve been annoyed by the ending of season 3’s “Parasites Lost,” in which Fry evicted his worms despite them doing nothing wrong. This time around, the worms get to stick around in the loving home they’ve built for themselves.
It’s a lot like the ending to the classic episode “Love and Rocket,” in which a bunch of “love radiation rays” destroy a whole lot of planets filled with innocent people. “But one planet was at exactly the right distance to see the romantic rays, but not be destroyed by them: Earth,” Zoidberg monologues. “So all over the world, couples stood together in joy.” At the end of “Parasites Regained,” it’s Leela and Nibbler standing happily together, problems solved. And it only took a little bit of mass murder to pull it all off.