LOS ANGELES -- Ouch! The goofballs of MTV's insane stunt show "Jackass" have taken their masochistic shtick to the movies, complete with skull injuries, embarrassing nudity and pain -- lots and lots of pain.

For these guys, jumping out of a tree wearing underwear attached to bungee cords is more than a way to get an eyeball-popping wedgie -- it's a dismissal of anyone who ever scolded someone to "Behave!"

Jackass-in-chief Johnny Knoxville says the goal of his kamikaze comedy is to make people laugh, and he has no message besides, "Don't try this at home."

After inflaming critics with the crude concept, Knoxville quit the MTV show last year after less than a year on the air because he thought the joke had run its course. "Jackass: The Movie" is his encore -- a way to celebrate his contribution to the retreating boundaries of taste. The movie opened Friday.

Knoxville, whose real name is P.J. Clapp, started the "Jackass" phenomenon while testing safety equipment for a column in a skateboarding magazine, and says it's just an extreme form of slapstick. Asked why it caught on, he says he doesn't want to "suck all the fun out of it by pontificating."

"It's always funny to see somebody get broke," he explained. "There's nothing funnier than an untalented stuntman, in my opinion."

Comic bits in "Jackass: The Movie" range from lamebrain silliness (running around naked in public) to "Candid Camera"-style pranks (renting a car and demolishing it in a crash-up derby) to injuries (falling off a skateboard on concrete steps) and gross-out antics.

Imitators burned

The TV show -- which still airs in late-night reruns -- drew criticism that it encouraged dangerous behavior. After Knoxville wore a fireproof suit and allowed himself to be set ablaze and "roasted" on a grill, a few imitators were severely burned when they defied the show's disclaimers and performed their own variations on the stunt.

A 15-year-old in New Hampshire told investigators that he was inspired by "Jackass" to ignite lamp oil on a 12-year-old friend, who suffered second-degree burns.

"I just wish parents would take a little more time to see what their kids are watching and see what their kids are doing," Knoxville said.

His 6-year-old daughter, Madison, is forbidden from watching all but the tamest "Jackass" pranks, Knoxville says.

So what's so appealing about self-inflicted suffering?

It may be that the macho stunts on "Jackass" strike a chord with some viewers at a time when cultural changes have diluted traditional ideas of masculinity, says David Savran, a theater professor at The City University of New York.

"The humiliation proves you're a man, proves you're tough," he said. "Plus, so many people now are so hungry after celebrity that they will do almost anything to get on TV."