Invader ZIM - Season 1 - Eps 7: Dark Harvest
When Dib finds out that Zim has no human organs, he attempts to exploit Zim’s ailment of head pigeons to get the skool’s nurse to examine Zim in hopes she will see the truth. However, when Dib blurts his plan out to Zim, Zim develops a device that will permit him to switch objects for organs, in which he begins to steal the organs of his fellow classmates in order to appear more human in time for his appointment at the nurse’s office.
About Invader ZIM

Title: Invader ZIM
First Air Date: 2001-03-30
Last Air Date: 2006-08-19
Status: Canceled
Rating: 8.429/10 (from 392 votes)
Language: EN
Seasons: 3
Total Episodes: 46
Network: Nickelodeon
Genres: Animation, Sci-Fi & Fantasy, Comedy, Kids
Production Companies: Nickelodeon Animation Studio
Synopsis
Zim dreams of greatness. Unfortunately, though, he's hopelessly inept as a space invader. Desperate to be rid of the annoying Zim, his planet's leaders send him on a mission to infiltrate Earth, providing him with leftover, cobbled-together equipment. To their consternation, Zim succeeds in setting up a base on Earth and infiltrating human culture, posing as a human child as he plots the planet's downfall. Only Zim's archnemesis, Dib, recognizes that Zim is an alien, and of course, nobody believes Dib's claims.
Cast

Richard Steven Horvitz
Zim (voice)

Andy Berman
Dib (voice)

Rosearik Rikki Simons
GIR (voice)

Melissa Fahn
Gaz (voice)

Lucille Bliss
Ms. Bitters (voice)

Rodger Bumpass
Professor Membrane (voice)

Kevin McDonald
Almighty Tallest Purple (voice)