It’s true that Monsters vs. Aliens couldn’t be considered a B-movie in the classic sense of the term. The “B’s” of 50 years ago were made on the cheap strictly to fill out a double-feature, exactly the opposite of what you get with the marketing push an outfit like DreamWorks Animation gives to its big-budget releases. But it’s also true that the gold standard of Pixar has sometimes been used as a club by well-meaning critics—hand raised here to plead guiltyas-charged—to beat down the computeranimated Johnny-come-latelies. Family-friendly adventures with a bit less ambition can succeed on their own terms—even if those terms involve little more than decent jokes and nifty set pieces.

Like any decent B-flick, this one begins with a weird, glowing meteorite striking the earth. In its path is Susan (Reese Witherspoon), who takes a direct hit from the luminescent rock on her wedding day, and winds up growing to 50 feet tall at the altar. Within a matter of minutes, she finds herself captured by the government and transferred to a super-secret holding facility, where all the weird beings that could inspire public panic are kept: the half-man/half-insect Dr. Cockroach (Hugh Laurie); the unfrozen Missing Link (Will Arnett); jovial gelatinous mass B.O.B. (Seth Rogen); and the freaky colossal hamsterbug called Insectosaurus. They’re outcasts, but who ya gonna call when the megalomaniacal extraterrestrial Gallaxhar (Rainn Wilson) threatens the planet?

Co-directors Rob Letterman (Shark Tale) and Conrad Vernon (Shrek 2) set the stage early for what they’re all about here with a prologue that includes an Antarctic researcher playing with a paddle-ball game, the red rubber sphere launching outward at the audience. It’s a wonderfully silly trick, and it’s evidence of how little the filmmakers—including a gaggle of screenwriters—expect all this to be taken seriously beyond its ability to get an audience to shriek with glee.

They accomplish their modest goals by keeping a steady focus on two goals: make ’em laugh, and keep it fast. The former is a function of some savvy casting as much as anything else. Rogen provides the brainless appeal of the oozing B.O.B., while the cocky-but-thick President of the United States is rendered in the inimitable cocky-but-thick tones of Stephen Colbert. And it was a small stroke of genius giving the villain role to Rainn Wilson, who has perfected the art of misplaced arrogance as Dwight on The Office. Sure, the eye-rolling pop-culture gags occasionally make an appearance—seriously, Harold Faltermeyer’s Beverly Hills Cop theme?— but they play a far less significant role than the character-based humor.

And considering this is a science-fiction adventure, it’s pretty important that the action sequences click as well. The showcase segment involves a battle between the monsters and Gallaxhar’s giant robot from San Francisco to the Golden Gate Bridge, taking advantage of the area’s unique geography for some thrilling chases. The climactic battle on Gallaxhar’s ship proves equally lively, rarely sacrificing momen tum for a cheap gag. Whenever it seeks strictly to entertain, Monsters vs. Aliens doesn’t miss a beat.

The only thing wrong with the film, in fact, is that it’s not entirely ready to commit to its straightforward guns. Taking its cue from the master recipe for all 21st-century family animation, it feels obliged to include a “be true to yourself” character arc, as Susan struggles to reconcile her new stature with her desire for a simple life with her simple fiancé (Paul Rudd). It might have worked better had the filmmakers committed to making a story that was actually set in the 1950s, instead of in the present. Building a narrative on a modern woman tasting liberation feels more than slightly retro—and not in a good way.

What works about Monsters vs. Aliens is when it is retro in a good way. It doesn’t try too hard to nudge its adult viewers with knowing references, or to pander to its young viewers with bodily functions.

There’s a place for the movies that touch our souls—and there’s a place for the ones where it’s OK just to let them “B.”

MONSTERS VS. ALIENS