There's a bit in the new "Night at the Museum" movie where "The Thinker" comes alive to catcall a nearby hottie of a statue. "Hey baby, check out the gun show goin' on over here," he struts, flexing his killer biceps. "Boom, Boom. Firepower!"

The scene sends my fourth-grader and her friends into hysterical fits of laughter every time they re-enact it, complete with New York accent just like Rodin's naked guy.

But why, of all the schtick in that movie — and in their lives — does it crack them up, along with so much other playground humor?

Sounds of flatulence from boy armpits and mouths. Anything involving "butts" for the kindergarten set. From a giggly first-grader I know: "Why did the chicken cross the road? To get to the other chicken." Greasy grimy gopher guts. The double entendre. The innuendo. Wack screen names of Web-crazed tweens and teens. "Family Guy."

Should parents consider any real value in kid humor? The pee-pee remark they've heard 18,000 times? The knock-knock joke that never ends?

THERE'S VALUE IN IT

Some "humor experts" think they should.

Take the hand in the armpit gag that sets some adult teeth on edge.

"The measure of it as a really good joke is whether or not you spew milk out of your nose. That's an interesting metric. What it does is capture you by surprise. It's uncontrollable laughter that causes you a physiological anomaly, and a painful one I might add," said Ed Dunkelblau, a big teddy bear of a man with a Ph.D. who works regularly with schools and Fortune 500 companies preaching the gospel of humor.

Dunkelblau, a psychologist, said the sustainability of some kid humor (knock-knock jokes will never go out of style) is part oral tradition, part desire for social interaction and acceptance, and part emotional release.

So potty jokes and the simulated sounds of flatulence should be encouraged in the young?

"Absolutely. Not during a math test, necessarily, but there are too many places in our world right now where children have to be serious," Dunkelblau said. "We forget that humor, laughter and play are vital to our existence."

That doesn't mean boundaries aren't helpful to steer young people away from humor that hurts or excludes, especially in less-supervised settings such as school playgrounds.

"Kids learn to build relationships through humor and laughter," Dunkelblau said. "There are ways to play and be humorous that don't cost anybody self-esteem."

What's funny to kids is one thing. Why is another matter.

Research shows that children respond to humor long before they can fully understand language or develop long-term memory. It also shows that humor is present as one of the early fundamental cognitive processes, which goes a long way in explaining what makes peek-a-boo ad infinitum so amusing to babies.

"I think we're hard-wired to laugh," Dunkelblau said.

HEALTHFUL DEFIANCE

Two top funny guys from American Greetings, Pat Sandy and Brian Cleary, see kid humor as a triumph of language and one of the earliest acts of defiance — both of which should be celebrated as necessary and healthy.

"We do the same thing as grown-ups. We show off our vocabularies," said Cleary, senior editor of the company's Web site. "It's funny when a child can decode that a word means two different things, like 'Irish' and 'Irish you a Happy St. Patrick's Day.' A knock-knock joke is like a peacock showing off its feathers."

Sandy, senior program director of alternative cards for American Greetings, said parents should consider a well-tuned sense of humor an asset to their children.

"A kid who is really hopped up on humor shows a sign of intelligence at an early age," he said. "Yes, there's a time and a place for everything, but armpit farts and booger jokes show an ability to take incongruent devices and bring them together."

While some parents fret over the magnetic pull of scatological and off-color humor, social worker and mom Devra Renner falls into the laid-back camp. Co-author of the book "Mommy Guilt" and a parenting consultant in northern Virginia, Renner said parents tend to forget what made them laugh — and how good it felt — when they were young.

"Consider how many times you've heard a parent ask a giggling child, 'What's so funny?' " said Renner, who with sons ages 8 and 13 has heard her share of that armpit thing.

"But if we give up the adult definition of what 'fun' is and remember what was fun when we were kids, I think many parents would be amazed at their newfound ability to once again discover just what it is that's so damned funny."