The ultimate tribute to cheesy 1950s science fiction — with its flying saucers, ray-guns and little green men — already exists and it's called "Mars Attacks." Tim Burton's homage to a duff genre was so wonderfully over-the-top, it's pretty hard to imagine anyone topping it, but Dreamworks Animation gives it a try in their latest offering "Monsters vs. Aliens," an animated film which pairs '50s sci-fi tropes with retro monster movie characters from such "classics" as "The Blob," "The Creature from the Black Lagoon" and "Attack of the 50-Foot Woman."

Directed by Rob Letterman and Conrad Vernon, who previously brought us "Shark Tale" and "Shrek 2," "Monsters vs. Aliens" is — like all Dreamworks animation — much more focused on pop-culture gags than its character-driven Pixar competitors. And, as usual, the results are pretty hit or miss, some absolutely brilliant gags mixed in with a lot of whiffs.

The story begins in Modesto, Calif., where a young bride named Susan (voiced by Reese Witherspoon) is about to wed her self-absorbed TV weatherman fiance Derek (Paul Rudd) when she's struck by a glowing meteorite. She gets up, dusts herself off, and is all ready to say "I do" when she suddenly starts growing wildly, bursting out of her bridal gown and eventually right through the roof of the church, as everyone flees in terror. The men-in-black arrive, sedate her, and whisk her away to a secret government facility where she's locked up with a bunch of other monsters.