Blink and you could miss them.

Cameo appearances — sometimes the brightest spot in a two-hour-plus movie — are becoming increasingly popular, and actors like Will Ferrell (search), Andy Dick (search) and other funnymen are clocking minimum time to get maximum laughs at theaters.

"It's a really hip way to say 'I'm an edgy guy who doesn't need credit, I don't need a starring role to steal a picture,'" said Bill Hoffmann, entertainment columnist for the New York Post.

Actors may not get the top billing or multi-million-dollar paychecks, but uncredited character roles are memorable for bringing the element of surprise and a quick injection of humor into a movie.

Ferrell's recent cameo as Big Earl in "Starsky & Hutch" "stole the picture," said Hoffmann.

Although Ferrell probably got very little money for playing the sex-starved jailbird, he "gets credit overall by embedding himself in the minds of the American film-going public," according to Hoffmann. "It helps him down the road getting bigger paychecks in bigger films. It's like investing. You reap benefits later."

Andy Dick has a steady gig on ABC's "Less Than Perfect," but he is famous for popping in and out of big screen comedies. His quirky cameos have won big laughs in "Old School" (Garry the sex instructor), "Zoolander" (Olga the masseuse) and "Road Trip" (hotel clerk).

Sometimes a cameo is an original character appearing in a movie remake (Lou Ferrigno in "The Hulk," Jaclyn Smith (search) in "Charlie's Angels: Full Throttle," Paul Michael Glaser and David Soul in "Starsky & Hutch"). Other times, a celebrity in another field takes a turn in Tinseltown (Donald Trump in "54" and David Letterman in "Cabin Boy"). And sometimes celebs basically play themselves, such as when rapper Snoop Dogg was a rapper in "Old School."

In most cases these flashes of familiar faces titillate audiences by stuffing more stars into a picture.

"You pay your $10 to see a couple of big stars in a movie, then suddenly another star is on the screen," said Hoffmann. "Even in 'Gigli,' Al Pacino pops up in a tense five-minute scene, and he's the only good thing in that movie."

But a cameo can miss the mark if the actor doesn't click.

Movie fan Rhett Ursy of Seattle said he likes seeing stars pop up unexpectedly on screen, but only when they gel with the bigger picture.

"Character actors who bring a lot like Jerry Stiller in 'Zoolander' ... they have a purpose, you get why they are there," said Ursy. "Not like Patrick Swayze doing 'Dirty Dancing: Havana Nights.' That was just not necessary. It didn't add anything to the movie."

Getting the chance to step outside their usual roles is one reason actors do cameos, said Dana Polan, professor of cinema at the University of Southern California.

"They get to play with their image but not in a way that would be damaging," said Polan, who added that comedy is an ideal genre for cameos.

"Part of the problem of the cameo for other genres is they throw you outside of the story," she said. "You are noticing the actor and as the actor not as the role. You don't want to say, 'Oh that's Julia Roberts,' because it breaks down the story effect."

However, even in campy comedies having a big star pop in can go awry, according to Hoffmann, who said some roles should remain true cameos.

"Demi Moore should have kept quiet and not demanded a huge paycheck and starring credit for 'Charlie's Angels,'" he said. "Better to have people fall in love with you by themselves instead of having your PR people shove them down your throat — 'This is her big comeback!'"

But bust or bang, a cameo usually works to an actor's benefit.

"It's really a no fault thing," said Hoffmann. "If the film was great they say, 'I wanted to be in that.' If it's horrible they say they did it as a joke."