Monsters Vs. Aliens - Plot

Plot

Bride-to-be Susan Murphy (Reese Witherspoon) is struck by a meteorite on the day of her wedding to weather reporter Derek Dietl (Paul Rudd). Instead of killing her, the meteorite exposes her to the substance quantonium, causing her to rapidly grow to over 50 feet tall. Alerted to the meteorite, first by an Arctic base and then the priest at Susan's wedding, the military arrives and captures Susan. She is given the code name "Ginormica" and sent to a top-secret secure facility headed by General W.R. Monger (Kiefer Sutherland). There she meets her fellow monster inmates: B.O.B. (Seth Rogen), a brainless, indestructible gelatinous blob; Dr. Cockroach, PhD (Hugh Laurie), a mad scientist with the head and abilities of a cockroach; the Missing Link (Will Arnett), an amphibious fish-ape hybrid; and Insectosaurus, a massive grub that is even larger than Susan.

An alien named Gallaxhar (Rainn Wilson) detects quantonium radiation on Earth and deploys a gigantic robot probe to find it. After the robot lands the President of the United States (Stephen Colbert) attempts to make first contact with it by playing Axel F on a keyboard, but the attempt fails and the impervious robot begins destroying everything in sight. General Monger convinces the President to use his monsters to fight the robot instead. The monsters accept the mission when they are promised their freedom if they succeed. Arriving in San Francisco, Susan is chased by the robot over the Golden Gate Bridge, where the monsters defeat it.

Now free, Susan returns home and introduces her family to the monsters. They are quickly rejected, though, after innocently causing a neighborhood panic. Derek breaks up with Susan, claiming that he cannot be married to a freak since she would overshadow his career. At first devastated, Susan realizes that becoming a monster is an improvement on her life, and fully embraces her new role. Suddenly, she is abducted by Gallaxhar, who appears to kill Insectosaurus in the process. On Gallaxhar's spaceship, Susan escapes and chases Gallaxhar down, only to be lured into a machine that extracts the quantonium from her body, allowing her to shrink back down to her normal size. Gallaxhar then uses the extracted quantonium to power a machine that creates an army of his clones to invade the Earth.

With General Monger's help, B.O.B., Dr. Cockroach, and the Missing Link infiltrate Gallaxhar's spaceship, rescue Susan, and hot-wire the spaceship's power core, activating the self-destruct sequence. During their escape, Susan is cut off from her friends who are trapped in the power core. They tell her to save herself, but Susan instead finds Gallaxhar, who is trying to escape with the quantonium. She tries to force him into releasing her friends, but when he admits he cannot reverse the sequence, Susan instead takes the quantonium, restoring herself to giant size and saving her friends. The monsters leap out of the exploding spaceship and are rescued by General Monger on the back of the transformed Insectosaurus, who has metamorphosed into a butterfly.

The monsters receive a hero's welcome home. Derek tries to get back with Susan since it would benefit his career, but Susan rejects him by tossing him into the air like a doll. He is caught, swallowed and spit out by B.O.B. on camera. The monsters are then alerted to a giant snail named Escargantua attacking Paris and they fly off to face the new menace.