It's an elemental calculus: (Men) + (Women's clothing) = Funny. I have no idea why this is so, but it seems to be wired into our cultural DNA. Presumably there was a Cro-Magnon comedian 10,000 years ago who strapped on a pair of coconuts and the Paleolithic equivalent of a housedress and slayed 'em around the campfire one night. The genetic express runs from that through ''Some Like It Hot" and the Monty Python boys and ''Tootsie," right up to ''Big Momma's House 2," where it hits the wall and falls over.
Well, that's a little unkind. This belated sequel to the 2000 comedy that stuck Martin Lawrence in a flowered muumuu and several metric yards of latex padding is completely unnecessary but painless, like dentistry performed by mimes. Despite a PG-13 rating, it's fine for the family crowd -- there are little life lessons, broad jokes, a minimum of crotch hitting -- while still being lame enough that you'll probably want to wait for the DVD.
When last we saw LA-based FBI agent Malcolm Turner (Lawrence) he -- oh, who cares, that was six years ago. All you need to know is that Malcolm's wife, Sherrie (Nia Long), is eight months pregnant, a villainous tech CEO (Mark Moses) is about to unleash a computer virus that would allow terrorists to infiltrate America's top-secret computer networks, and Malcolm's ex-partner has just been killed following the lead. And the CEO needs a nanny.
Enter Big Momma, Malcolm's bumptious, bewigged alter ego. ''Big Momma's House 2" has nothing to do with logic as it waddles pleasantly down a well-worn path. The CEO turns out to be a nice guy workaholic (the real bad guys have him over a barrel), his wife (Emily Procter) an uptight nervous Nellie, and the kids (Kat Dennings as the rebellious teenager, Chloe Grace Moretz as the insecure tweener, twins Preston and Trevor Shores switching off as the hell-raising toddler) neglected and sweet. Their real problem, of course, is that they're white. In any case, Big Momma heads to the rescue, dispensing love and serious back.
Except for a bit where the hero/heroine finds him/herself in a ladies' locker room of a spa, Lawrence keeps the leering under control, and one or two honest low-rent laughs sneak out. (I'm thinking particularly of the lovelorn Chihuahua, and the scene in which Big Momma channels Bo Derek's slo-mo beach run in ''10.") In the end, though, the movie's geniality is counterbalanced by its total lack of originality. ''Big Momma's House 2" is ''The Pacifier" with a big fat transvestite instead of a big bald Marine, nothing more, nothing less. How long will they keep making this movie? Until you folks stop paying to see it.
Ty Burr can be reached at email@example.com.