Director Chris Wedge has said that, following the success of his 2002 animated feature “Ice Age,” he wanted to do something “bigger.” His new movie, “Robots,” is certainly that. The cast overflows with celebrity vocal talent, and every frame is crammed with meticulous detail. Sadly, it all amounts to a reminder that in Hollywood more can often be less. “Robots” is like a long day at an overcrowded amusement park: By the end you may feel less entertained than exhausted.

The movie tells the story of young robot Rodney Copperbottom (Ewan McGregor), who leaves his humble home in Rivet Town for the big city, where he hopes to get a job as an inventor for Big Weld Industries. Upon arriving, however, he discovers that the company’s legendary leader, Big Weld (Mel Brooks), has disappeared. Running the company in his place is ruthless corporate bottom-liner Phineas T. Ratchet (Greg Kinnear).

In an effort to increase profits, Ratchet has tossed out the company’s public-spirited credo and closed down the division that supplied spare parts for older robots. Instead, the company will now sell only expensive new upgrades (slogan: “Why be you when you can be new?”).Those robots who can’t afford the upgrades will simply wear out and become fodder for the subterranean scrap-metal business run by Ratchet’s diabolical mother, Madame Gasket (a cross-voicing Jim Broadbent).

Upping the emotional stakes, one such endangered “outmode” is Rodney’s own father (Stanley Tucci). So with the help of a comely junior executive (Halle Berry) and a group of robotic misfits known as the Rusties (Robin Williams, Drew Carey, Amanda Bynes), Rodney sets out to find Big Weld and put an end to the villains’ nefarious plans.

Twentieth Century Fox, which produced both “Ice Age” and “Robots,” has yet to develop a signature animated style. The former movie, with its intimate, character-driven story, seemed made in the mold of Pixar releases such as “Toy Story,” “Monsters Inc.,” and “The Incredibles.” “Robots,” by contrast, more closely resembles the ironic, pop-inflected style pioneered by Dreamworks (“A Shark’s Tale,” the “Shrek” movies). It’s not an improvement.

“Robots” is essentially a series of loosely strung-together set pieces – the Robot City train station, the gala ball, the battle with Madame Gasket – filled with knowing gags such as a robot who dances “the robot” and a public transit system closely modeled on the 1960s game Mousetrap. Indeed, the movie abounds with boomer and Gen-X nostalgia trips, including everything from Operation and the domino craze to “Rollerball” and the Survivor anthem “Eye of the Tiger.”

Beset on all sides by in-jokes, the characters never develop much beyond the automaton stage. In part, this is because the film’s robots just aren’t very visually expressive. One of the main thrusts of animation technology has been rendering human (and animal) faces ever more lifelike, capturing the way skin absorbs light or fur and fabric move through the air. “Robots” goes in the opposite direction, building its cast from metal sheets and spheres and cables. As a result, for all its technical wizardry, the movie looks a little primitive, almost like stop-motion animation, its robots sleeker descendants of Gumby’s Blockheads.

Worse, the film’s impressive cast – even small roles are voiced by the likes of Paul Giamatti, Dan Hedaya, and Dianne Wiest – were apparently hired more for their names than for their performances. Mr. McGregor is in optimistic whiz-kid mode as Rodney (like in “Moulin Rouge,” only whizzier), and Mr. Brooks brings comic avuncularity to Big Weld. But Ms. Berry, Mr Kinnear, and most of the rest barely have time to register at all.

The exception is Robin Williams, who after a decade of relative restraint is back in full schizo show-stopper mode, a la “Aladdin” or “Good Morning, Vietnam.” Mr. Williams reportedly ad-libbed much of his role as the robotic scavenger Fender, and it shows: He careens randomly from an impression of a Spanish toady to spoofs of “Braveheart” and “Singin’ in the Rain.” Some of it is amusing, but there are as many misses as hits, and a couple of the bits (the fashion photographer riff, the Britney Spears number) seem to have been borrowed from the Austin Powers movies. Moreover, there’s no real reason for Williams’s multiple-personality performance – he’s not playing a polymorphous genie or manic radioman this time – so it’s hard to shake the sense that he was cast simply to bring a little life into an otherwise mechanical enterprise.

It’s not enough. Mr. Williams’s frantic improvisations keep the film moving, but they can’t supply it with any real warmth or feeling. Like the tin woodsman that it parodies on more than one occasion, “Robots” can’t get around the fact that underneath its shiny exterior it has no heart.