Supermodel Kate Upton appears in an online Mercedes-Benz video in a low-cut top. An unknown man wakes up with his face covered in smeared lipstick and his hands bound in furry handcuffs in a Gildan Activewear clip. And “30 Rock” star Tracy Morgan seemingly curses in a spot for Kraft’s Mio flavored drops.

“Hey, can you say (bleep) on TV?” he asks in the spot titled “Bleep.”

Super Bowl advertisers no longer are keeping spots a secret until the Big Game. They’re releasing online snippets of their ads or longer video trailers that allude to the action in the Game Day spot.

It’s an effort to squeeze more publicity out of advertising’s biggest stage by creating pregame buzz. Advertisers are shelling out $4 million to get their 30-second spots in front of the 111 million viewers expected to tune into the game. But they’re looking for ways to reach even more people: About half of the more than 30 super Bowl advertisers are expected to have teaser ads this year, up from 10 last year, according to Hulu, which aggregates Super Bowl ads on its AdZone Web site.

“It’s a great way to pique people’s interest,” said Paul Chibe, chief marketing officer at Anheuser-Busch, which introduced snippets of one of its Super Bowl ads showing a woman in a shiny dress striding down a hallway with a beer. “If you create expectations before the game people will want to look for your ad in the telecast.”

There’s an art to teasers. Each spot, which can run from a few seconds to over a minute long, is intended to drive up hype by giving viewers clues about Game Day ads. But the key is to not give too much away. So marketers must walk a fine line between revealing too much – or too little – about their Super Bowl ads.

Taco Bell CEO Greg Creed said introducing a teaser helps people feel as if they’re “in the know” about the company’s Super Bowl ad before it airs. The company’s teaser shows an elderly man, who is also the star of its Game Day ad, doing wheelies in a scooter on a football field.

“On game day, we want people to say, ‘Shh, shh, shh. Here comes the ad,’ ” he says.

Some companies have been successful using Super Bowl teasers in the past. Last year, Volkswagen’s teaser that showed dogs barking “The Imperial March” from the Star Wars movie was a hit. In fact, it was almost as popular as the Game Day ad, which had a Star Wars-themed twist ending. Both the teaser and the ad each received about 16 million views on YouTube.com.

But other spots fall flat, or worse, are all but been forgotten once the mystery is revealed during the Big Game. For instance, Bridgestone put out several teasers for its Super Bowl ad last year. But the Game Day ad itself did not show up the USA Today AdMeter, which ranks the popularity of ads.

“It makes sense that people would want to get more mileage out of their ads than just a single viewing on the Super Bowl because of the cost,” said Barbara Lippert, columnist at mediapost.com. “But it’s a big risk. It can have a big reward, too, but what usually happens is the spots just don’t live up to the hype. The effect is amplified if you release it early.”

To be sure, no matter how carefully marketers try to control pre-game buzz, sometimes it gets away from them. Volkswagen, following its past success with “The Imperial March,” teaser, is facing some criticism this year.

On Monday, it released its Super Bowl ad showing a Minnesotan office worker who adopts a Jamaican accent because he’s so happy with his car. Some online columnists called it culturally insensitive because it shows a white man adopting an accent associated with black Jamaicans.

Volkswagen said the accent is intended to convey a “relaxed cheerful demeanor.”

Still, some ad experts say by releasing the ad early, Volkswagen might have spared itself backlash later. After all, now they have time to tinker with the spot before it airs.

“Even though it’s not a good ad, they managed to get as much attention this year as they did last year before the game,” Lippert, the ad critic, says. “It’s amazing to use America as their test kitchen, which they did.”

Here are some teasers on the Web:

Mercedes-Benz Kate Upton teaser: http://www.youtube.com/watch?v=uPq7jVGPs3g

Volkswagen’s “Get In. Get Happy” ad: https://www.youtube.com/watch?v=9H0xPWAtaa8

Gildan Activewear teaser: On the Web: http://www.youtube.com/user/GildanTV?v=_KIKjcMTKPk

Kraft’s Mio ad with “30 Rock’s Tracy Jordan: http://www.youtube.com/watch?v=eenSfU7YYnY

Budweiser Black Crown Lager teaser: https://www.youtube.com/user/blackcrownbeer