At New York's Central Park Zoo, a lion (Stiller), a zebra (Rock), a giraffe (Schwimmer), and a hippo (Smith) are best friends and stars of the show. But when one of the animals goes missing from their cage, the other three break free to look for him, only to find themselves reunited ... on a ship en route to Africa. When their vessel is hijacked, however, the friends, who have all been raised in captivity, learn first-hand what life can be like in the wild.