'Monsters vs. Aliens' The president enlists a motley crew of Monsters, confined in a secret government compound, to combat an alien robot and save the world from imminent destruction. With the voices of Reese Witherspoon, Hugh Laurie, Will Arnett, Seth Rogen, Rainn Wilson, Stephen Colbert, Kiefer Sutherland and Paul Rudd. Directed by Rob Letterman and Conrad Vernon. Also in Imax. Paramount Pictures, March 27.