The idea of the 50-foot woman has always presented men with conflicting instincts.

Would you run toward her  . . . or away?

And if you choose the former, what would you do when you got there? Certainly she has more of what men want than any other woman, but so much that it's bound to raise the issue of how you would, um, contribute to the relationship.

This raises questions of adequacy, which is why I suspect most guys would retreat, and why, in the old movies, the 50-foot woman is always knocking down electrical towers and snapping power lines. The imagery speaks for itself.

In "Monster vs. Aliens," the 50-foot-woman (actually 49 feet 11 inches) is also in 3D, and so the spectacle is even more staggering - 50 feet tall, and 10 feet deep!

But she's also strangely de-sexualized - clothed in a sporty unitard, given a blonde bob, and voiced by Reese Witherspoon, who will always be more perky than anything else.

Witherspoon's character is a happy bride-to-be whose wedding goes haywire when she ingests an alien substance that gives her immense size and power.

The U.S. government slaps a scary name on her - Ginormica - and locks her in Hangar 19, an Area 51-style secret compound with other government-held "monsters." There's a blue mass of jelly (Seth Rogen, typecast), a half-man, half-cockroach (Hugh Laurie), a froggish thing and a giant insect.

Movie buffs will recognize the motifs from old-timey sci-fi and horror titles. They are variations on "The Fly," "The Blob," "Mothra" and "The Creature from the Black Lagoon."

This is a quintessential DreamWorks Animation product - jokey, fast-paced riffing on stories and images from a Baby Boom past, received by adults as satire/nostalgia, and by their children as, well, just another action toon, with the added attraction of new-generation 3D (check your theater to make sure they've got the technology).

The action begins when a big-brained alien (Rainn Wilson) arrives looking for his missing power source, unleashing a robot on San Francisco. As a last resort, our cowardly president (Stephen Colbert) calls for the government-held monsters to take on the invading alien.

The story focuses on Ginormica. Initially ashamed of her size (her boyfriend leaves her), she comes to appreciate her literal empowerment, and we get a tidy lesson in self-esteem.

It's a predictable updating of the 50-foot-woman idea, but it doesn't go very deep. DreamWorks go for jokes first, action second, resonance third or not at all. They aren't out to topple Pixar. They're out to make money, and this jaunty movie will make plenty. *

Produced by L*sa Stewart, d*rected by Conrad Vernon and Rob Letterman, wr*tten by Maya Forbes, Wally Wolodarsky, Rob Letterman, Jonathan A*bel and Glenn Berger, d*str*buted by DreamWorks.