'Monsters vs. Aliens' has high-energy humor

Classic creatures from the 1950s get a high-tech makeover, with a healthy amount of attitude, in the 3-D animated "Monsters vs. Aliens."

The Blob, The Creature from the Black Lagoon, The Fly – they're are all here, led by The 50-Foot Woman, who's now 49 feet, 11 inches, as voiced by the diminutive Reese Witherspoon. (Animation, by the way, is a great fit for her, and for both the crispness and sweetness in her voice.)

Far from being menacing, they're optimistic misfits who just want to be loved and understood. Rather than destroying each other, they're loyal friends who've been trapped together as government test subjects, only to be unleashed on the world when an alien invasion requires their unique powers.

It's an enormously clever concept – no pun intended – with a choice voice cast. Who else but Seth Rogen could play a lovable blue blob named B.O.B., who always has a smile on his gelatinous face? Will Arnett essentially revives his hilariously cocky-but-clueless "Arrested Development" character, Gob Bluth II, as the half-fish, half-ape Missing Link, and Hugh Laurie lends his rich voice to the British mad scientist Dr. Cockroach.

Just seeing the words "And Stephen Colbert as The President" during the opening titles is good for a laugh, especially given the comic's faux run for the White House from his home state of South Carolina.

And the laughs keep coming steadily from there. Directors Rob Letterman ("Shark Tale") and Conrad Vernon ("Shrek 2"), working from a script from about a half-dozen people, maintains a high energy throughout, although the explosive climax feels bombastic and repetitive. Far more effective is the way this motley crew comes together.

Witherspoon's Susan is a simple woman from Modesto, California, who is about to marry pompous TV weatherman Derek (Paul Rudd). On their wedding day, as Susan dreams of honeymooning in Paris and Derek obsesses over an anchor audition in Fresno, a meteor hits Earth, exposing Susan to galactic gloop that turns her into a giant with a shock of white hair. (And as she grows, her wedding gown rips and clings to her in sexy ways – but there's nothing too racy here on any level. "Monsters vs. Aliens" is decidedly PG, with any vestiges of antagonism softened for the sake of family-friendly comedy. It could have used a bit more edge.)

The military, led by Gen. W.R. Monger (Kiefer Sutherland), scoops her up and sticks her in a holding cell along with B.O.B., Link, Dr. Cockroach and a goofy, 350-foot (106-meter) bug named Insectosaurus. (Their back stories, rendered in run-down film clips, are a nice nostalgic touch.) They also rename her Ginormica, which gives her a self-esteem boost when she needs it most.

An alien attack, led by the megalomaniacal Galaxhar (Rainn Wilson), forces the monsters into the streets of San Francisco. A showdown between Susan and Galaxhar's prime weapon, a clunky retro robot, is beautifully detailed as it causes the windows on downtown office buildings to rumble and shatter. Greater thrills come when the monsters fight the robot on the Golden Gate Bridge in an old-school, B-movie battle.

While bright and colorful, the three-dimensional effects in these situations never really inspire a sense of awe. Rather, they provide a tangible sense of depth but fall short of completely immersing you.

The movie's also playing in IMAX 3-D – maybe that's a more satisfying sensory experience, one that makes you feel as if you truly are on another planet.