If sheer cleverness were everything, "Robots" would be the best computer-animated cartoon yet. The movie invents an entire robot world in which all things mechanical take on a life force of their own. Dazzling landscapes feature Rube Goldberg contraptions and visual gags that turn our world on its head. Yet, unlike the very best CG animation, "Robots" doesn't quite connect with the emotions and humor for which one yearns in cartoons. The film is just a bit too ... well, mechanical.

"Robots" comes from director Chris Wedge and Blue Sky Studios, which gave us the frisky prehistoric cartoon "Ice Age" in 2002. The Blue Sky trademark now is clear: slapstick comedy and manic energy. It's Looney Tunes times four (at least), with the screen crammed with more visual gags than eye or brain possibly can register, which undoubtedly means repeat theater visits by youngsters and huge sell-through in the video/DVD market. "Ice Age" took in more than $176 million, and "Robots" should repeat if not surpass those totals.

As is Wedge's habit, his simple, likable (or unlikable) characters mostly are a collection of running gags. There is a robot named Fender (voiced by an equally manic Robin Williams), whose body parts fall off at inopportune moments, and his kid sister, Piper (Amanda Bynes), who is a tightly wound ball of energy. Some characters truly are marvelous. Jim Broadbent of all people raises his voice a few octaves to play the villainous Madame Gasket, an erratic design of mismatched parts that seem to leak red grease.

The screenplay, designed by David Lindsay-Abaire and the comedy-writing team of Lowell Ganz & Babaloo Mandel, envisions a world inhabited entirely by robots. Unlike "Monsters, Inc." no rationale is given for such a world. Nor do we understand how it came to be invented, no Big Clang theory as it were. It just exists. Cups of oil replace cups of coffee and a fire hydrant can talk back to a dog.

Our hero is Rodney Copperbottom (Ewan McGregor), assembled and raised by parents to believe anything is possible. He is fed a similar notion through TV broadcasts by Bigweld (Mel Brooks in a kind and gentle mode), the master inventor who rules the only corporation that seems to exist. The door always is open to any new inventor, Bigweld declares. So when Rodney leaves his hometown for Robot City with invention in hand, he is shocked to find that door firmly shut.

The back story is vague, but it seems that Madame Gasket and her sleekly robotic son, Ratchet (Greg Kinnear), somehow have shunted Bigweld aside. They scheme to take off the market all spare parts needed by the robot citizens to live and function. Instead, they manufacture only expensive "upgrades." Thus, many otherwise fine robots who can't afford these upgrades find they have become "outmodes," vulnerable to city sweepers that can snatch them off the street and deposit them at Madame Gasket's Chop Shop.

So Rodney, Fender and Fender's gang of outmodes -- this includes eternal pessimist Crank Casey (Drew Carey), big-hearted Lug (Harland Williams) and Diesel, who lacks a voice box -- set off to challenge the greedy rulers of the massive corporation. Along the way, Ratchet's female assistant with a great 'bot, Cappy (Halle Berry), rebels and joins the good guys.

There are marvelous set pieces: A cross-town express flings Rodney and Fender through the mechanical metropolis like a cross between a monorail and roller coaster. Bigweld surfs a sea of dominos. The climatic battle between the corporation's robotic army and the retooled and refitted robot misfits explodes into a frenzied spoof of action-movie fights.

Much of the animation is spectacular. Even the colors somehow have a metallic look. Yet, as complex as this imagined world is, Wedge keeps his characters rudimentary. Thus, audiences never develop much emotional attachment to any of them. The emphasis here is entirely on the timing of gags and a steady flow of action.