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.
Source: http://www.imdb.com/title/tt0351283/plotsummary