This is an amusing animated movie. We are introduced to the monsters through a young woman named Susan (voice of Reese Witherspoon), who is struck by a meteorite and transformed into a white-haired giant that the government calls "Ginormica". She's taken to a secret holding facility where all the other monsters are kept, such as Dr. Cockroach (Hugh Laurie), the Creature from the Black Lagoon-like Missing Link (Will Arnett) and B.O.B (Seth Rogan), an amorphous blue blob. And there's
the Godzilla sized Insectosaurus, which may be the funniest looking giant monster I have ever seen. The movie is renting out simply to see this creature.
When a huge alien robot starts walking through San Francisco, the monsters are recruited to stop it, with the promise that they'll be freed from prison. They do stop it,though the Golden Gate bridge is destroyed. However, there are lots more robots where this one came from. The four-eyed alien Gallaxhar (Rainn Wilson) wants a rare substance called Quantonium, which is the same stuff that transformed Susan into Ginormica. He starts producing clones of himself for the invasion of Earth--and it's up to the monsters to stop him.
I enjoyed this movie, though I felt that they didn't have any "real" monsters in this, as none were terrifying or a threat to people. In fact, after I saw this I wanted to watch MAD MONSTER PARTY.