In a more innocent time when police corruption meant simply stealing rather than shooting unarmed civilians, Frank Serpico went under cover to expose the deeds of some of his unscrupulous fellow officers. Sidney Lumet's movie about this hero--who had to leave his country to take us residence in Switzerland--was not without humor, one of the most amusing parts focussing on the title character disguised as a Hasidic man and more. The cop in "Big Momma's House" may be like the champion of Lumet's 1973 movie in one way. He is the bearer of false identity, but lacks the variety enjoyed by Serpico. While "Serpico" featured an authentic blend of comedy and drama, in making "Big Momma's House, director Raja Gosnell aims strictly at our funny bone.

Gosnell's aim is off. "Big Momma's House" gives even the notion of summer movies a bad name. Utilizing one of the oldest and moldiest species of comedy--female impersonation--Gosnell is not even good at creating anything original. Ripping off a scene far better done by Tony Curtis and Marilyn Monroe in "Some Like It Hot" and generally filching from the modern forerunner of the genre, "Mrs. Doubtfire," this one is merely a showcase for the talent of a crackerjack comic, Martin Lawrence, but proves only that Lawrence can be far better when he's just himself and not decked out as a 400-pound cliche.

The simple plot, which is nothing more than an excuse for foisting one unfunny sitcomish bit after another on the audience, could fit right into a six o'clock sitcom. Even the outdoor scenes look as though they were wheeled in for use by CBS or NBC TV. In this tale, FBI Agent Malcolm Turner (Martin Lawrence), together with his competent but comical sidekick (Paul Giamatti), is on the trail of an escaped killer (Terrence Howard). The FBI guesses that the perp is looking for his former girl friend, Sherry (Nia Long), who may herself be on the run and headed for the house of her estranged relative, Big Momma.

Robin Williams had a far superior script and concept to work with in Chris Columbus's 1993 film "Mrs. Doubtfire." Lawrence, by contrast, is left with the most banal exertions at physical comedy. Disguised as Big Momma--who outweighs him by about 250 pounds--Lawrence is given the most predictable responsibilities, obligations which include fixing his ample bosom when it gets out of alignment, cooking pork chops with a couple of sticks of lard and half a bottle of Crisco, and supporting a rubber mask whose construction is hardly as adept as the ones used by Tom Cruise and company in "M:I-2." The mask begins to tear, the pork chops are burned to a crisp, the boobs go a-bobbin' and Lawrence ponders how he can make a hit on Sherry when Sherry simply does not have romantic feelings for her Big Momma.

The scenes that have some possibility of functioning are one which finds Nia Long cuddling up in bed with the incognito FBI agent (who must convince the comely young woman that what she feels in bed is only a flashlight) and another involving the alleged Big Momma giving a sadistic karate instructor his comeuppance. There is also some snappy gospel singing and a sentimental ending that turns Agent Malcolm Turner from a man who has acquired the hostility of the townsfolk into the citizens' hero after the agent's unconvincing four-minute "testimony" to the congregation. Rent Ted Demme's 1999 movie "Life" to see what Lawrence is really capable of doing when he has a story that juxtaposes genuine poignancy with good, broad comedy.