Fan Casting

On Planet 51, green extraterrestrials live peacefully in a society reminiscent of the United States during the 1950s. One day, a mysterious spacecraft lands in the town of Glipforg. NASA astronaut Charles T. "Chuck" Baker emerges from it and is shocked to find the planet inhabited. Chuck escapes to the town’s planetarium, where he meets teenage alien Lem, who works there part-time. Realizing Chuck is not a threat, Lem agrees to help return him to his spacecraft before command module Odyssey in Planet 51's orbit departs for Earth and leaves him stranded. Planet 51's army, led by the paranoid General Grawl, arrives to inspect the spacecraft. Grawl, after Chuck's MP3 player is accidentally started, deduces that the astronaut is an alien invader bent on turning planet’s population into zombies, and a manhunt ensues throughout Glipforg. Lem enlists the help of his best friend Skiff, a science fiction aficionado with conspiracy theories about the so-called "Base 9", to hide Chuck away from the army. During his efforts to conceal Chuck, Lem inadvertently upsets his neighbor and crush Neera, who believes the alien is friendly, and is also fired from his job when his boss discovers Chuck. In Lem’s room, Chuck reunites with a dog-like NASA probe called Rover, which freed itself from the army’s base after tracking Chuck with a GPS and headed for the city and which befriends a small, domesticated Xenomorph. After the army searches Lem’s home for traces of the alien, Lem and Skiff move Chuck to a comic book store Skiff works at, where Glipforg’s news station manages to capture Chuck acting out references to Earth’s pop culture, which is misinterpreted as alien threats. After escaping the store from the invading army, Grawl has Chuck’s spacecraft moved to a secret location. Chuck is later captured by Grawl’s forces during a festive movie premiere in town, and is slated to have his brain removed by alien scientist Professor Kipple. When Lem defends Chuck, Kipple deems him a zombie minion. Chuck, resigned to his fate, pretends to release Lem from his "mind control" and is taken away with Rover to Base 9, which Grawl inadvertently reveals. Lem gets his job back, but is determined to rescue Chuck. Joined by Skiff, Neera, her younger brother Eckle, and Rover (who escaped the army again), Lem tracks down Base 9's location in the desert to a gas station where Skiff inadvertently opens a gate to the underground base. They free Chuck from Professor Kipple and find his spacecraft, but they are cornered by Grawl and his forces. Bent on eliminating Chuck, Grawl reveals has the base rigged to explode. Lem tricks the General into activating the countdown. Enraged, Grawl attempts to shoot Lem, but misses and the stray bullet ignites an explosive, causing Grawl to be trapped under debris. Chuck rescues Grawl before launching his spacecraft into Planet 51’s orbit, escaping Base 9’s destruction. After admiring Planet 51’s view from space, Lem successfully asks Neera out on a date, while Grawl expresses his gratitude to Chuck for saving him. Chuck returns his friends home and allows Rover to stay behind with Skiff, who has connected with the probe, and bids Lem and the rest of Glipforg farewell before launching back into space, but the last seconds of the film reveal that the little Xenomorph befriended by Rover is on board.