A wispy-thin but suitably quick-witted homage to the science-fiction genre, "Monsters vs. Aliens" kicks off with a black-and-white, 1950s-inspired version of the Dreamworks logo, with the fishing boy sitting on the "D" letter sucked up by a flying saucer above him. A sort of "Invasion of the 50-Foot Woman" crossed with the spoofy tone of Tim Burton's "Mars Attacks!," the film presses on to tell its own story while referencing everything from "E.T.: The Extra-Terrestrial," to "2001: A Space Odyssey," to "Close Encounters of the Third Kind," to even "Spaceballs." Kids may not get all of the in-jokes in this luminously computer-animated feature—those will be better appreciated by the grown-ups in the audience—but they will be swept up all the same by the fantastical action sequences and ragtag of goofy yet sweet characters.

On her way to the wedding chapel to marry news anchor Derek Dietl (voiced by Paul Rudd), Susan Murphy (Reese Witherspoon) is struck by a falling meteorite. Before she has time to say her vowels, she transforms into a platinum-haired, super-strengthed, 49-foot-tall version of her former self. Captured by a secret government agency and taken back to their underground lair, Susan is given a new identity as "Ginormica" and befriends fellow imprisoned monsters Dr. Cockroach, Ph.D. (Hugh Laurie), fishman The Missing Link (Will Arnett), furry 350-foot grub-cum-butterfly Insectosaurus, and the brainless, gelatinous B.O.B. (Seth Rogen). The lot of them are given a mission—to defeat a giant alien-controlled robot who has landed near San Francisco—with the promise to be set free if they succeed. More dangerous elements are afoot, however, as maniacal extraterrestrial Gallaxhar (Rainn Wilson) prepares to invade the planet and steal all of its quantonium, the most powerful substance in the universe.

As an animated picture, "Monsters vs. Aliens" is not up to par with the best of Pixar and Disney, but it is a step in the right direction for a studio that too often has relied in the past on flash-in-the-pan pop-culture references and gags over heart and good, old-fashioned storytelling. Directors Rob Letterman (2004's "Shark Tale") and Conrad Vernon (2004's "Shrek 2"), along with a mouthful of screenwriters—Maya Forbes & Wally Wolodarski (2008's "The Rocker"), Rob Letterman, and Jonathan Aibel & Glenn Berger (2008's "Kung Fu Panda")—keep things moving at a brisk pace and make sure not to overcomplicate the plot. The title pretty much explains it all, and the moral of self-acceptance against adversity is one that makes its well-meaning case without becoming too serious or preachy.

The voice talent of Reese Witherspoon (2008's "Four Christmases") helps to shape and develop Susan into a tough, brave, likable heroine, while Seth Rogen (2008's "Pineapple Express") is a scene-stealer as comic relief B.O.B., a blob whose lack of a brain renders him cheerfully confused the bulk of the time. There is a very funny scene where Susan is first introduced to her new living quarters by the agency—a bleak, empty cell with a poster of a kitten on the wall that reads, "Hang in there!"—and a cute bit involving not-quite-lovebirds Katie (Renee Zellweger) and Cuthbert (John Krasinski) witnessing the crash-landing of the robot beyond a moonlit orange grove. The climactic battle on board an alien spacecraft minutes away from self-destructing serves its purpose, but it is a bit of an anticlimax in comparison to the film's central show-stopping set-piece set on the streets of San Francisco and culminating on the Golden Gate Bridge. This elaborate sequences is so genuinely exciting and sparklingly animated that there is really nowhere to go afterwards but down.

"Monsters vs. Aliens" doesn't slow down enough to really build much emotion beyond its own aesthetic spectacle, and this leaves the film decidedly slight. Suffice it to say, a new modern animated classic has not been born. As comedic family pics go, however, it is enjoyable while it lasts, and the Real-D version that will be showing in selected theaters continues to make the case for how much better today's 3-D technology has become (even if the format as a whole is still unnecessary).