Scorch Supernova (voiced by Brendan Fraser) is a heroic alien on a mission to rescue captured babies from the Gnarlachs. He rescues them just in time before the Gnarlachs wake up. Scorch returns to Planet Baab where he is known as a famous hero and works at BASA with his older brother Gary (voiced by Rob Corddry). Gary's son Kip (voiced by Jonathan Morgan Heit) is a big fan of his uncle Scorch. Soon, Gary receives a message from Lena Thackleman (voiced by Jessica Alba), the head of BASA, that Scorch will be sent to the "Dark Planet" (the Baabians' name for Earth) due to a SOS call. Scorch decides to go to the Dark Planet, as he already made a press conference and contacted his sponsors. However, Gary opposes as Scorch is not serious and no alien has ever returned from the Dark Planet. After further arguing, Gary finally says that he won't be helping Scorch and quits BASA before Scorch himself fires him. Gary then goes home to his wife Kira (voiced by Sarah Jessica Parker) and Kip only to find out that Scorch has already gone to the Dark Planet, while Kip is watching it on live TV in excitement. Scorch arrives on Earth and lands in the desert and finds a 7-Eleven convenience store but mistakes an airdancer for a dying being. Scorch is then tranquilized and captured by Shanker Saunderson (voiced by William Shatner), the malevolent general of the US Army, and is taken to "Area 51" where aliens from other planets are held. Knowing that this has happened, Kip wants to go rescue Scorch but Gary discourages him. Kip is angry and goes to his room. Gary goes to Kip's room to apologize only to find him going to try and save Scorch. He rushes to BASA with Kira wearing his rocket boots. They arrive to find Kip is about to take off in a ship. Gary manages to cancel the launch sequence at the last minute, but re-activates the sequence so he himself can rescue Scorch. As soon as he arrives, his ship immediately activates a self-destruct sequence, but Gary manages to escape. He arrives at the same store that Scorch arrived at earlier. Gary enters the store, but is spotted by its owner, Hawk Hawksbit (voiced by Steve Zahn), and his older brother and assistant, Hammer (voiced by Chris Parnell). Although both feared Gary, the two men realize that Gary isn't hostile and offer him a Slurpee giving Gary a brain freeze. Afterwards, Shanker's men break into the store, tranquilzes Hawk and Hammer, and capture Gary, taking him to Area 51. Gary is taken to Shanker's office where he is quickly removed after Shanker receives an incoming call from Lena who's revealed to be an ally of Shanker's as she has sent him a powerful source known as "blubonium". Gary is placed in a cell hall with other alien geniuses including Doc (voiced by Craig Robinson), Io (voiced by Jane Lynch), and Thurman (voiced by George Lopez) who tell Gary that various human technology has been invented by them for Shanker to rip off and sell to all of Earth so he will release them from Area 51. With these technologies, Shanker had made deals with companies like Apple Inc., Facebook, Google, and Pixar. Gary reunites with Scorch, but is again annoyed by his conceited behavior. After a food fight in the cafeteria, the aliens make their way to "the peace shield." Meanwhile, Lena captures Kira, who stayed at BASA and tried contacting Gary on his rescue mission. Lena then reveals her plan to give a lifetime supply of blubonium to Shanker. After Shanker reveals the blubonium, Gary unintentionally provokes Scorch into stealing it after stating its dangerous power. While being chased, Scorch destroys the blubonium, causing Shanker to freeze him and orders Gary to fix the blubonium and reveals that he's going to destroy all alien planets in the universe with a laser ray using the blubonium. Shanker thinks that all aliens are hostile just because a trio of grey aliens' spaceship (accidentally) killed his father (voiced by Michael Dobson) in 1947. Gary fixes the ray with help from his new friends, but Shanker goes back on his promise and freezes him instead. The other aliens discover Shanker's true intentions when he tries to destroy Baab with the laser ray and mutiny, knocking out Shanker's henchmen. It is revealed that Gary did not put the machine together completely and it malfunctions, destroying itself before it can destroy Baab. With Gary and Scorch released from their icy prisons by the machine alongside the other frozen aliens, the brothers, Doc, Thurman, and Io escape Area 51. With help from Hawk and Hammer, Gary and company locate Scorch's spaceship in a trailer park. Meanwhile, back on Baab, Kip frees his mother Kira, who stops and subdues Lena after the latter took off with the blubonium shipment. US Air Force jets chase Gary's saucer, but Kip guides him through and manages to evade and destroy the jets. However, Shanker, wearing Scorch's robotic suit, uses a tractor beam to stop the ship in midair. Gary and Scorch jump out and manage to get the suit off Shanker which causes them all to fall to their doom. While freefalling, Scorch and Gary reconcile before they and an unconscious Shanker are rescued by the grey aliens. After Gary knocks out Shanker, the grey aliens take the latter away to deal with him. Scorch, Gary, Doc, Thurman and Io return to Planet Baab where Gary is reunited with his family. Scorch is greeted as a hero, but gives the credit to his brother which the citizens of Baab celebrate. Scorch then embarks on his toughest mission yet: marrying his girlfriend, Gabby Babblebrook (voiced by Sofía Vergara). Hawk, Hammer, and the grey aliens are also present at the wedding.
