At a combined weight of nearly 1,000 pounds, the Fat Boys are only a half a ton of fun. And that goes for their big, bold burlesque show "Disorderlies," a screwball comedy that was especially written for them. It's a vulgar, lowest-common-denominator caper, but the Fat Boys are such sweet-natured cutups they win over even sourpusses.

Better known as masters of rap, the tremendous trio is new to acting -- so new in fact that the Boys haven't quite got it down pat. But they do show a knack for slapstick a` la Larry, Curly and Moe -- the Three Huges, slapping each other silly, dropping their pants, belly-flopping villains into submission, cannonballing into pools.

They make being fat seem funny, but they don't have the Stooges' precision timing yet. With their monstrous girth -- by comparison Nell Carter is a Vogue model -- they lack comic grace. Slapstick is a kind of dance but the Boys are limited to jiggling while they rap, swaying precariously like wide loads on a mountain road. Miraculously they never crush each other.

The movie has a little music and one internal video that's not too cleverly worked into the plot by writers Mark Feldberg and Mitchell Klebanoff. They toured with the stars so they could tailor the movie's characters to their personalities. And, sure enough, they came up with the Fat Boys as the Fat Boys.

They play inept but endearing orderlies who lose their jobs in a crummy Brooklyn hospital when they're caught consuming cakes -- 60 of them. Food comedy gives over to action after they're hired by Anthony Geary, as compulsive gambler Winslow, who plans to pay off his debts by snuffing his rich uncle. Winslow chooses the disorderlies in hopes that their incompetence will kill Ralph Bellamy, playing the grumpy avuncular geezer Albert Dennison.

Here, the story shifts to Dennison's manicured Palm Beach estate for some crass culture clash comedics ("Watch out Palm Beach, you're in for a treat/The Fat Boys have landed, blue bloods meet street"). It's a clash far below the level of "Trading Places," which "Disorderlies" remotely resembles. But it's also more benign.

As it happens, the disorderlies -- Mark (Prince Markie Dee) Morales, Damon (Kool Rock-ski) Wimbley and Darren (The Human Beat Box) Robinson -- prove good medicine, devoted to their patient. Mr. Dennison improves when the Boys give him plenty of pizza and a spin at an all-night roller-skate disco. Soon Albert is warning the prissy Winslow to "chill out ... Step off." Winslow is forced to plot a murder more menacing.

Geary, the soap opera superstar, is snarly in his thankless part, but Bellamy, a trouper at 83, moves from curmudgeon to homeboy almost joyously in the company of his irrepressible costars. Robinson, the Beat Box, is especially bubbly.

Michael Schultz, who signed the Boys while working with them on the set of his street musical "Krush Groove," also directs "Disorderlies." And it is blatantly ramshackle, a shameless, blameless excuse to showcase these hefty weights. What an incredible bulk. Disorderlies, rated PG for nudity, is at area theaters.