Monsters vs. Aliens (2009)

“Monsters vs. Aliens” cheerfully converts the two major sources of cinematic terror — invaders from outer space and inhuman, ungodly terrestrial creatures — into wacky, goofy, familiar figures. The movie, directed by Rob Letterman and Conrad Vernon from a many-authored script, comes out of DreamWorks Animation and offers the latest twist on the easygoing, parodic formula refined in the studio’s “Shrek” franchise and last year’s “Kung Fu Panda.”

Just as “Shrek” and its successors pushed aside the sweet enchantment of traditional fairy tale movies in favor of belching and winking (with a saving spoonful of sugar at the end), so does “Monsters vs. Aliens” turn fright and apocalypse into strenuous, noisy, 3-D fun.

The film, like “Coraline” and “Bolt,” tries to take 3-D technology beyond gimmickry and to make it the basis for a new kind of visual spectacle. Since not all theaters are equipped to show the movie this way, it has to work in its flat version as well, and perhaps partly as a result, the effects are often subtle, noticeable less when objects or characters jump off the screen than when they move laterally across it.

“Monsters vs. Aliens” is no better than most family-friendly animated entertainment, but there does seem to be more of it. Everything looks bigger and rounder. The environment is deeper and thicker. The blob of blue goo with one eye and Seth Rogen’s voice is more palpably, quiveringly slimy.

That blob, named B.O.B., is an entirely predictable supporting character in a movie like this: the dumb one whose off-the-wall observations and behind-the-beat non sequiturs provide a steady stream of mild and easy laughs. Somehow Mr. Rogen, whose next live-action vehicle opens in a few weeks, keeps postponing the moment when we tire of him. His affable stoner vibe is the best thing in “Monsters vs. Aliens.”

Though perhaps not in itself enough reason to see it. Don’t get me wrong: the movie is not terrible. On the contrary, it is a highly competent, smartly engineered delivery system for the very clichés it pretends to subvert.

The most surprising of these may be the romantic-comedy convention of an interrupted wedding, an apparent disaster that will of course turn out to be a blessing. This is because the would-be bride, Susan (Reese Witherspoon), is a charming young woman betrothed to a self-absorbed cad (Paul Rudd), whose eventual comeuppance provides a nice, sequel-enabling coda after the crazy action sequences are done.

These involve a battle between some monsters, including Susan — who, I should mention, has a mishap that makes her grotesquely gigantic, though since the movie’s sense of scale is wildly inconsistent, it’s hard to say just how gigantic — and what is technically only one alien, a many-legged, many-eyed intergalactic imperialist voiced by Rainn Wilson. San Francisco is destroyed, and a few other kind of cool things happen, but in spite of its striving for visual novelty, the movie is curiously unmemorable, partly because nearly all of its humor depends on your having seen something like it before, even if you haven’t.

So in addition to Mr. Rogen’s dumb blob, there is a brainy scientist-monster (Hugh Laurie), a vain, macho monster (Will Arnett) and a speechless, fuzzy, gigantic monster that provides the film’s gratuitous hat-tip to the Japanese anime tradition.

These earthbound monsters live in government-imposed quarantine, overseen by a general with a buzz cut and a drill sergeant’s bark, provided by Kiefer Sutherland. Everyone goes whirling through the air, fires off some wisecracks and generally has a good time. You probably will too, even if you feel a little cheated in the end.

“Monsters vs. Aliens” is rated PG (Parental guidance suggested). It has some semiviolent action sequences with implied fatalities.

MONSTERS VS. ALIENS

Opens on Friday nationwide.

Directed by Rob Letterman and Conrad Vernon; written by Mr. Letterman, Maya Forbes, Wally Wolodarsky, Jonathan Aibel and Glenn Berger, based on a story by Mr. Letterman and Mr. Vernon; edited by Joyce Arrastia and Eric Dapkewicz; music by Henry Jackman; production designer, David James; produced by Lisa Stewart; released by DreamWorks Pictures and Paramount Pictures. Running time: 1 hour 34 minutes.

WITH THE VOICES OF: Reese Witherspoon (Susan/Ginormica), Seth Rogen (B.O.B.), Hugh Laurie (Dr. Cockroach, Ph.D.), Will Arnett (the Missing Link), Kiefer Sutherland (General W. R. Monger), Rainn Wilson (Galaxhar), Paul Rudd (Derek Dietl) and Stephen Colbert (the President).