The Nightmare Begins
S1E1
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"Bow down and prepare for DOOM!"
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.