June 2, 2000 | How much mileage can a movie get from a single sight gag? Only a middling amount, judging from Big Momma's House, a textbook example of a one-joke comedy.

At once overbearing and insubstantial, this formulaic farce invites us to laugh again and again (and again) at the spectacle of Martin Lawrence in cartoonish female drag as a rotund septuagenarian. If just reading about that is enough to give you the giggles, consider yourself part of the film's target audience. But heed this consumer alert: The funniest parts are available for free in trailers and TV spots.

Lawrence plays Malcolm Turner, an FBI agent who obviously shops for make-up and rubber masks at the Impossible Missions Force commissary. He makes his entrance in heavy disguise as an elderly Korean gentleman during an undercover operation. Later, while conducting a stakeout in a small Georgia town with his longtime partner (Paul Giamatti), he demonstrates an even greater mastery of disguise by passing himself off as a corpulent grandmother nicknamed - yes, you guessed it! - Big Momma.

Malcolm dons a dress and affects extra poundage to gain the confidence of Big Momma's beautiful granddaughter, Sherry (Nia Long, much better than she has to be), who's on the run with her young son, Trent (Jascha Washington). Sherry seeks refuge with Big Momma to avoid Lester (Terrence Howard), Sherry's cold-blooded bank-robber ex-boyfriend, who broke out of prison to retrieve a stash of cash. Sherry insists she knows nothing about any stolen money, and Malcolm comes to believe her. Even so, his FBI superiors suspect she is, at the very least, an accessory after the fact. But that's only because Lester has used her as an unwitting accomplice.

It comes as little surprise that Sherry falls in love with Malcolm - when he's not in drag, he poses as a neighborhood handyman to woo her - and it's no surprise at all when the real Big Momma (Ella Mitchell) inconveniently returns home. Actually, there's nothing at all surprising in Big Momma's House, a movie that proceeds at the unhurried pace of someone ticking off chores on a things-to-do list. Big Momma uses salty language? Check. Big Momma beats wise-guy teens at basketball? Check. Big Momma shakes her booty at Sunday service? Check. And so it goes.

Director Raja Gosnell (Never Been Kissed) served as editor on Mrs. Doubtfire, which no doubt allowed him ample time to memorize bits of comic business that he attempts, with mixed results, to replicate here. Lawrence is no Robin Williams, but he gets the job done with exuberant physicality and razor-sharp timing. It helps a lot that he remains extremely likable even when he's doing stale shtick, or when the slapstick seems more frantic than funny.