Cast of Monsters vs Aliens

Reese Witherspoon voices Susan Murphy, who transforms into the giant creature Ginormica.

Seth Rogen provides the voice for B.O.B., a gelatinous, brainless character.

Hugh Laurie voices Dr. Cockroach Ph.D., an intelligent insect transformed into a scientist.

Will Arnett voices The Missing Link, a half-fish, half-ape creature.

Kiefer Sutherland provides the voice for General W.R. Monger, a military leader.

Rainn Wilson voices Gallaxhar, the main antagonist of the film.

Paul Rudd voices Derek Dietl, Susan's fiancé who becomes concerned about her transformation.

Stephen Colbert provides the voice for President Hathaway, who addresses the nation's crises.

Julie White voices Wendy Murphy, Susan's mother.

Jeffrey Tambor voices Carl Murphy, Susan's father.

Amy Poehler voices the Computer, which assists the characters.

Ed Helms voices the News Reporter, covering the events unfolding in the film.