Eddie Murphy reputedly is a shy man, which probably explains his love of hiding behind eccentric characters and layers of prosthetics.

This has led to some sublimely hilarious movie moments, most notably the Klump family dinner from "The Nutty Professor."

"Norbit" once again finds Murphy donning a fat suit, but this time the payoff isn't nearly as satisfying.

Here he essays three roles. First there's the title character, a skinny/nerdy accountant reared in an orphanage who, after losing the love of his life (she was adopted) falls into the clutching, cellulite-heavy arms of the overbearing (and grossly overweight) Rasputia (Murphy again.)

Murphy also plays Mr. Wong, the operator of the orphanage, who speaks in Pidgin English and is a good guy despite thoughtlessly spouting racially insensitive observations (Wong apparently is unaware that he is himself a raging stereotype of the comical Oriental).

The screenplay by Jay Sherick and David Ronn (from a story by Murphy and his brother, Charles Q. Murphy) finds the adult Norbit living a life of misery. Rasputia is greedy, vain, gluttonous, egotistical and physically and emotionally abusive. Also, she's cheating on Norbit with her skinny dance instructor (Marlon Wayans).

Henpecked at home, Norbit is terrorized at work by Rasputia's three thug brothers (Terry Crew, Clifton Powell, Mighty Rasta) whose construction company pretty much runs the town.

Then Norbit's childhood love Kate (Thandie Newton) reappears, intent on buying the orphanage so that she can continue operating it for the benefit of children. This puts her at odds with Rasputia and her brothers, who want to turn the property into a strip club. Further complicating matters, Kate has a fiance (Cuba Gooding Jr.) who unbeknownst to her has a history of siring children and abandoning their mothers.

It doesn't require a film degree to figure out how this is going to play out.

"Norbit" has some very funny physical comedy, but it doesn't always go down easily since the target is usually Rasputia's intimidating weight. The film goes out of its way to make Rasputia reprehensible on almost every level, but in the end we're reduced to laughing not at the character but at her obesity.

It's a complete turnaround from the overweight but endearing Sherman Klump character Murphy played in "The Nutty Professor." In that film we were asked to sympathize with the plight of a "big" man. "Norbit," though, is mean-spirited at the expense of fat people. I could deal better with mean-spiritedness if the film were better written and directed. But the picture's humor is hit and miss.

Technically, at least, the film is a marvel. The scenes of Eddie Murphy acting with Eddie Murphy are so seamless and convincing that after just a few minutes you buy entirely into the idea that Norbit, Rasputia and Chan are distinct individuals.

Now all they need is a decent story.