Earthworm Jim - Season 2 - Eps 3: Darwin's Nightmare
Bob, the Killer Goldfish creates an device that sucks the "evolutionary energy" out of anything that it wraps around. Jim and Peter are made into idiots by it, and remain idiots for a large percentage of the episode.
About Earthworm Jim

Title: Earthworm Jim
First Air Date: 1995-09-09
Last Air Date: 1996-12-14
Status: Ended
Rating: 7.2/10 (from 30 votes)
Language: EN
Seasons: 3
Total Episodes: 23
Network: The WB
Genres: Action & Adventure, Animation, Comedy, Sci-Fi & Fantasy, Kids
Production Companies: Flextech Television Limited, Universal Cartoon Studios, Shiny Entertainment, Universal Animation Studios, AKOM Production Company
Synopsis
Jim was a multi-celled life form happily burrowing through the topsoil. His life changed in a flash when an extraterrestrial super-suit fell out of the sky. Instantly transformed from a 98 gram weakling into a muscular worm endowed with superpowers, extraordinary strength and the ability to leap incredible heights and distances, the suit renders him invulnerable. Earthworm Jim - daring defender of Earth, the cosmos and everything in between!
Cast

Dan Castellaneta
Earthworm Jim (voice)

Jeff Bennett
Peter Puppy / Narrator (voice)

Jim Cummings
Psy-Crow / Bob the Killer Goldfish (voice)

Kath Soucie
Princess What's-Her-Name (voice)

Charlie Adler
Professor Monkey-for-a-Head (voice)

Edward Hibbert
Evil the Cat (voice)

Andrea Martin
Queen Slug-for-a-Butt (voice)

John Kassir
Snott / Henchrat (voice)