“Little Man” is the latest effort from the Wayans brothers, the guys responsible for “White Chicks” and the first two pictures in the “Scary Movie” series. And it’s just as dumb as its trailers and TV ads make it look.

But if you’re willing to follow the press-kit instructions of Shawn Wayans to “Take your brain out of your head, sit down and just have a ball,” there are some laughs inside this preposterous story he cooked up with his brothers, co-star Marlon and director Keenan Ivory.

Like “White Chicks,” this one’s an impossible-to-take-seriously mistaken-identity picture. In the earlier film, a pair of African-American cops go undercover as young, very rich white women in the Hamptons. Yeah, sure.

This time, a 2-foot-6-inch just-released-from-prison jewel thief masquerades as a toddler to try to retrieve a diamond that he’s heisted and stashed in a woman’s purse.

Marlon, or at least his head, plays the little tough guy, Calvin Sims. His partner Percy P (Tracy Morgan) picks him up at the prison gate and immediately takes him on a mission to steal the Queen Diamond from a jewelry story. The little felon initially pulls off the job, but when the alarm starts ringing and the thieves find a police boot on their car, they head off on foot.

In a nearby market, they encounter Darryl (Shawn Wayans) and Vanessa (Kerry Washington), a couple quarreling over whether to have children. Calvin dumps the jewel in Vanessa’s purse. To get it back, the genius criminals dress up Calvin as a toddler and leave him in a dog basket at the couple’s door.

Desperate to be a dad, Darryl immediately brings the little guy in and starts treating him as his own — and as a 2-year-old. If you can get by that, there are plenty of funny moments, many of which are telegraphed in the advertising for the picture.

However, if you’re not willing to massively suspend your disbelief, which is a trick if you bother to think about what you’re watching at any time, “Little Man” is inane at best.

Some skill that has gone into “Little Man.” Marlon’s head is composited on the body of a child actor. Obviously, that means that the entirety of his acting has to be done with his face, and he’s impressive in that sense.

Director Keenan Ivory Wayans also keeps the picture going at a breakneck pace, so even when jokes don’t work — and plenty of them flop — there’s not much time before the next attempt at a gag pops up.

The ending of “Little Man” is just as stupid and impossible to believe as the rest of the movie. But by that time, either you’ve bought into the Wayan brothers’ brand of stupid humor or you’ve checked out of this one.

The success of the “Scary Movie” pictures and “White Chicks” is evidence enough that plenty of moviegoers will fall into the first category. But if you want to use your brain in the theater at all, avoid this picture.

Reach L. Kent Wolgamott at 473-7244 or at kwolgamott@journalstar.com.