The real father of Maggie from "The Simpsons" is revealed in "Starship Poopers". He is also an alien voiced by Harry Shearer. Which planet is he from?
Treehouse of Horror IX: "Treehouse of Horror IX" is the fourth episode in the tenth season of the American animated television series "The Simpsons". Treehouse of Horror IX:  This is the ninth "Treehouse of Horror" episode, and, like the other "Treehouse of Horror" episodes, contains three self-contained segments: In "Hell Toupée", Homer gets a hair transplant and is possessed by the spirit of an executed criminal; in "Terror of Tiny Toon", Bart and Lisa are trapped in a special, extremely violent episode of "The Itchy & Scratchy Show"; and in "Starship Poopers", Marge reveals that Maggie is the product of a one-night stand with the alien Kang. Kang and Kodos:  Kang is voiced by Harry Shearer and Kodos by Dan Castellaneta. Kang and Kodos:  They are aliens from the fictional planet Rigel VII and appear almost exclusively in the "Treehouse of Horror" episodes.
Rigel VII