Scorch Supernova (Brendan Fraser) is an alien on a mission to rescue captured babies from the Gnarlachs. He rescues them just in time before the Gnarlachs wake up. Scorch then returns to Planet Baab where he is known as a famous hero and a love interest for anchorwoman Gabby Babblebrook (Sofía Vergara) while at BASA his brother Gary (Rob Corddry) works. Gary’s son Kip (Jonathan Morgan Heit) is a big fan of his uncle Scorch. Soon, Gary receives a message from Lena Thackleman (Jessica Alba), the head of BASA, that Scorch will be sent to the “Dark Planet” (Earth) due to a SOS call. Scorch decides to go to the Dark Planet. 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 (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 General Shanker Saunderson (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. When Gary flips Kip’s blanket open, he sees Kip’s dog and his window is open. Knowing that Kip is 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, but re-activates the sequence so he himself can rescue Scorch. He soon arrives on the Dark Planet. As soon as he arrives his ship immediately activates a self-destruct sequence, but Gary manages to get out. He arrives at the same store that Scorch arrived at earlier. Gary enters the store, but is spotted by two owners, Hawk (Steve Zahn) and Hammer (Chris Parnell). Both Gary and the two men were freaked out and try to hide from each other. After the owners realize that Gary is not a hostile alien, they offer him a Slurpee. Gary takes it but drinks it too fast and gets brain freeze. Afterwards, Shanker’s men break into the store and capture Gary, taking him to Area 51.