The superheroes have flown. Send in the clowns.

Sure, there have been a few jokers out there this summer besides the one in "The Dark Knight." But with all the flashy comic-book derring-do at the multiplex, they've been easy to overlook. But Steve Carell, Mike Myers, Eddie Murphy, Adam Sandler and Will Ferrell have all offered up cinematic frivolity with varying degrees of success.

However, their tried-and-true tomfoolery will soon seem as quaint as vaudeville routines as two of the most-anticipated and potentially genre-altering summer comedies in years open within a week of each other this month.

Coming off the Judd Apatow production line tomorrow is "Pineapple Express," which pairs "it" goofball of the moment, co-writer Seth Rogen, with his "Freaks and Geeks" bud James Franco. They're potheads on the run from thugs — think hard-core action with a bad case of the munchies.

Next week, it's "Tropic Thunder," filmed on Kaua'i, which lampoons over-earnest '80s war movies and inside-Hollywood stupidity. Featured is an elite force of funnymen headed by director/co-writer/co-producer Ben Stiller, Jack Black and Robert Downey Jr. There's even a disguised weapon of mass hilarity: Tom Cruise, in bald cap and blubber suit, as an out-of-control studio executive.

"Pineapple Express" is up there with "The Big Lebowski" and Sean Penn in "Fast Times at Ridgemont High," says Rolling Stone critic Peter Travers. "It's 'Superbad' seven years older with the same friendship idea. You get the feeling these men will not grow up, ever."

As for "Tropic Thunder," Travers says, "It's Ben Stiller at his smartest, laughing at Hollywood and himself, with Cruise dropped in the middle with his peak performance."

BREAKING THE MOLD

On the surface, the shaggy Cheech and Chong update and the cartoony "Platoon" spoof are as disparate as the size of their budgets — $25 million for "Express" and at least $100 million for "Thunder."

Yet they do have commonalities: Asian drug gangs, a deep disregard for political correctness, "bromantic" overtones of male bonding and newcomer Danny McBride, a first-class stooge who slays audiences every time he pops up in either movie.

And both films are signposts to where barrier-breaking big-screen comedies are heading. Back in the '80s, the summer laughs came supersized in such PG blockbusters as the "Ghostbusters" films and "Back to the Future." In the '90s, such gawky guys as "Saturday Night Live" grads Mike Myers (the "Austin Powers" series), Adam Sandler ("Big Daddy") and Ben Stiller ("There's Something About Mary") took command.

But this decade has been all about breaking the rules with shocks that go beyond the hair-gel grossouts in "Mary." In fact, the explicit sexual high jinks that came back into vogue with Apatow's "40-Year-Old Virgin" and "Knocked Up" no longer are quite so superbad. What's cool now is excessive violence that borders on the Tarantinoesque, the sound of gunfire accompanying ear-scorching obscenities.

Even Apatow, whose other projects rarely feature AK-47s and fiery explosions, was taken aback by the level of bloodshed in "Pineapple Express." His explanation: "It's the video-game generation. I say, 'We've gone too far,' and Seth just laughs and says, 'What are you, 100 years old?' "

It's all about capturing the attention of males 18 to 25, the most-coveted and easily distracted of all moviegoers. Or those who simply act like they are still 18-25 and can relate to these emotionally stunted comedy heroes.

"The hard R is directed at teenage boys of all ages," says Travers. "It says, 'This isn't going to be safe.' They push it to the limit."

Such as when Franco's dealer peddles his wares to grade-school kids or kicks Rosie Perez's dirty cop right where it counts. Or when Downey's pugilism-prone Aussie actor goes full-metal Method, resorting to blackface and a ghetto accent to portray an African-American soldier.

RISKIER FUNNY BUSINESS

Blame it on "Borat." "It opened up the door for films to again tackle political issues," Yale film professor Ron Gregg says of Sacha Baron Cohen's mock-doc assault on sacred cows, stereotypes and exposed body parts that collected $128.5 million in 2006.

"When Hollywood dealt with war directly last fall, it alienated audiences," he says. "Now comedies are starting to deal with national concerns outside of family and romance, like Sandler's 'You Don't Mess With the Zohan' and 'Harold & Kumar Escape From Guantanamo Bay.' We can laugh at the insanity."

Or as Todd Jackson, a humor writer who runs the comedy site Dead-Frog.com, says, "If you make people laugh and think, they like it. You can be smart about being stupid. People will let you get away with more."

While "Tropic Thunder" is more keen on taking well-aimed pot shots at the industry that feeds it rather than mocking the madness of war, "Pineapple Express" begins with a black-and-white prologue that subversively suggests none of the mayhem that follows would have happened if marijuana were legalized.

As shown by the poor reception to Myers' "The Love Guru" and Murphy's "Meet Dave," audiences aren't in the mood to play it safe. They require comedies with an edge, a sense of transgression. "My students talked endlessly about 'Borat,' Gregg says. "They went to 'Juno' over 'Knocked Up.' They are looking for novelty."

Making silly faces and doing a wacky accent is no longer enough. "Comedy used to be more about characters who were fish out of water or just weird," Jackson says. "Now they are dealing with the reality at hand, being more true to the situation."

Though their attitudes reflect unsettled times, "Pineapple Express" and "Tropic Thunder" had long gestation periods before reaching the screen. Stiller told www.ComingSoon.net earlier this year that he had the idea when he was shooting the Steven Spielberg epic "Empire of the Sun" in 1987.

"That's when all these Vietnam movies were being made," he said. "It was a time when all actors were going away to fake boot camp and talking about these incredible experiences that they had and how it really changed their lives. There was something there that seemed funny to me."

As for the over-the-top violence, including strewn guts and a bloody decapitation, Stiller felt he had to reflect the language and gore inherent in the movies he was satirizing. The thinking was, he said, "we should then at least have fun with it since we're going to have to be an R."

Meanwhile, "Pineapple Express" pays homage to the odd-couple action comedies of the '80s — "Midnight Run", "48 Hrs.," "Running Scared," "Beverly Hills Cop" — where raucous humor mingles with lethal gunplay.

But it was the Quentin Tarantino-scripted "True Romance" from 1993 that provided the inspiration for the story.

"I was watching 'True Romance' on laser disc, that's how long ago it was," Apatow says. "I always thought Brad Pitt was hilarious playing a crackhead and wished the guys were chasing him instead. I thought about potheads who think it is harmless to smoke it, and it would be funny if leaders of a pot cartel were as murderous as coke dealers."

In other words, "It's fun to see a Cheech and Chong film with Jerry Bruckheimer action."

MORE ACTION LAUGHS

For some reason, the studios decided to open two R-rated action comedies just seven days apart. While it might be a friendly rivalry — Apatow wrote for Stiller's 1992 Fox TV show, and they teamed up on 1996's "The Cable Guy" — Paramount and Sony apparently have been playing chicken with the opening dates. "Thunder" blinked first, shifting from a Friday (Aug. 15) to a Wednesday (Aug. 13). Then "Express" moved from a Friday (Aug. 8) to this Wednesday.

In any case, it's likely that both of the much-hyped comedies (their adults-only red-band trailers have been online since spring) will own the box office in August. Excitement for one just might feed into the other.

"Based on what we're seeing on our message boards and all over the Web, the buzz on both of these titles is really high," says Matt Atchity, editor in chief at Rotten Tomatoes, which tallies critical opinions of films. "It's going to be that end-of-summer last hurrah for moviegoers. Many will see 'Pineapple Express,' which will probably be No. 1 that weekend, and then turn around and see 'Tropic Thunder' the next. A one-two punch."

There are at least five other chucklefests of different sizes and interest opening this month. But Apatow sees it as only a positive. "There's a little bit of a tie-up on the runway, but as a comedy fan, there's nothing better on Earth than to have this many."