Universal Pictures

Will Ferrell as Dr. Rick Marshall.

Though it's rated PG-13, "Land of the Lost" has the heart and soul of a 10-year-old boy. This latest Will Ferrell showcase combines dinosaurs, potty jokes and mildly leering humor -- topics of interest at most any boy's sleepover.

Directed by Brad Silberling, it's based on the 1970s kids show of the same title. Ferrell trots out his trademark character -- the bumbling, clueless guy who triumphs despite his shortcomings. This time, he's Dr. Rick Marshall, a scientist on the brink of travel from one dimension to another.

Not everyone, including Matt Lauer (who makes a couple of cameos), buys Rick's theories. However, Holly, played by Anna Friel, is a disciple. She brings the good doctor evidence that there's a dimension that allows the past, present and future to coexist.

Off they go to a tacky roadside attraction run by a huckster named Will. Danny McBride plays the entrepreneurial bubba, and he makes Jason Lee on "My Name Is Earl" look like a Kennedy relative.

A warning to Ferrell: This McBride guy gets all of the stingy laughs in this misconceived Ferrell showcase.

Will the redneck takes the two scientists into a tunnel water ride, and the trio launches through a portal to another dimension.

They first encounter a brand of primates and rescue a little monkey-person named Cha-Ka. Played by Jorma Taccone, he's a frisky little rascal with enough bad teeth to keep him from being cute.

In this new world, airplanes collide with Viking ships, dinosaurs live with early humans and the ice cream man pops up to feed the ravenous reptiles.

Despite the movie's lack of belly laughs, it has an appealingly cheesy, surreal quality, including a drug trip that could have come straight from "Easy Rider." The big question is, does this kind of thing belong in a movie that's supposed to be kid-friendly? And while we're on the subject, do some of the sexual references belong here as well?

Meanwhile, Dr. Rick becomes the hate object of a vindictive Tyrannosaurus rex, and a tribe of lizard men threatens to breach the dimensional barrier and conquer the Earth.

Silberling (who has an undistinguished resume) and his writers strive mightily for farce and parody. Old-movie cliches are lovingly ridiculed, and there are overt visual references to "King Kong" and "The Wizard of Oz." Friel, an engaging actress, winds up looking like Dorothy Gale before the last dinosaur halitosis is exhaled.

The movie is unapologetically silly, but that's not its main problem. It struggles most when it calls for genuine wit and big-budget gags that don't require biological excretions.

Ferrell's one-trick pony is getting tiresome, and his latest character is larded with odd characteristics. Why is Rick's binge eating important to the story? Why does a brilliant man act so stupid? We know, we know: to advance the story. But still.

Ferrell's kind of hero who is blessed with a lack of self-awareness may be this generation's Jerry Lewis. Ferrell can be funnier than Jerry, though he still manages to impart the same childish qualities (only not as shrill). If he keeps on putting out this kind of dumb comedy, he, too, may be honored with France's Legion of Honor.