Kristin Chenoweth, Sarah Michelle Gellar and Charlie Sheen are all vying for the same job on Super Bowl Sunday.

Each will try to get it done in a different way. Gellar will display amazing range, going from frightened out of her wits to calm and confident – all in the space of 30 seconds. Chenoweth will use quirky humor to get people laughing quickly, working with a range of talented dogs to assist her with the task. And Sheen will utter a single line that he hopes will keep people riveted to their screens.

The three actors play big roles in three different Super Bowl commercials. Gellar will hold forth for Procter & Gamble’s Olay. Chenoweth takes to the ad field for Avocados of Mexico. And Sheen makes a pivotal cameo for Kraft HeinzPlanters.  While the use of celebrities in these big annual Madison Avenue pitches is as familiar as the football they support, the pressure on each actor to help their specific ad stand apart from dozens of others featured during the Super Bowl broadcast is fresh every year.

“You have a company that is relying on you for 30 seconds of airtime to make an impact in a very crowded marketplace,” says Gellar, in an interview.

That’s not the only burden placed on familiar actors during the Super Bowl. Millions of dollars are at stake. CBS, which will broadcast Super Bowl LIII from Atlanta on Sunday, is seeking between $5.1 million and $5.3 million for a Big Game ad package this year. The celebrities are often called upon to serve as ambassadors for the social messages or benefits associated with the products the marketers are trying to sell.

And there’s a chance the commercial in which they star might circulate for a long time – even decades. Ask “Mean” Joe Greene, the former defensive tackle for the Pittsburgh Steelers, who once won hearts in an iconic ad for Coca-Cola that was featured in Super Bowl XIV in 1980. Or Clint Eastwood, who told viewers of Super Bowl XLVI in 2012 that it was “halftime in America.” Of course, the spot could flop. Jeff Bridges, who will reprise his role as “The Dude” from the 1998 film “The Big Lebowski” in a Super Bowl ad this year for Anheuser-Busch InBev’s Stella Artois, left audiences puzzled in 2015 when he appeared in a Super Bowl ad for web-services company Squarespace and chanted “Om” so a couple could stay asleep.

Actors might want to tread carefully when considering whether to take part in a Super Bowl spot, no matter how alluring the prospect. “It’s no secret that using a celeb is purely about borrowing equity. So, as a celeb, you must decide who gets to borrow not just you, but more importantly your fans. Truth is, the more disconnected you are from the product you’re selling, the more unsettling it is to them,”  says James Bray, executive creative director at the large Arnold advertising agency. “They may love you, but they may not love Pepsi, Chevy or Stella Artois for a host of reasons. So, when brands borrow your millions of valuable followers, be aware that some won’t be returned in the same condition.”

Even so, celebrities are in high demand for the event. On Sunday, viewers will see Bridges and Sarah Jessica Parker for Stella Artois; Serena Williams for Bumble; Ludacris for Mercedes-Benz; Steve Carell, Cardi B and Lil Jon for Pepsi; Chance the Rapper and the Backstreet Boys for Doritos; and Christina Applegate for Mars’ M&M’s, among others.

Spotting celebrities in ads is “part of the attraction” of watching the event, says Allison Miazaga-Bedrick, brand director for M&Ms, in an interview.  Bringing familiar names to the commercials “gets those eyeballs,” she adds. “We are aware of the power of having not only a good commercial that delivers a message that is fun and light-hearted, but having a face that people know and can relate with,” says Alvaro Luque, CEO of Avocados from Mexico, entering its fifth year as a Super Bowl advertiser.

There’s more than just money to be gained from a Super Bowl berth. There’s broad recognition from people who may not have seen an actor’s latest work or most popular TV series or film. There’s a chance to burnish a cause that might be close to a celebrity’s heart. And there’s an opportunity to make an impression among friends and family.

“I thought, well, in some places in my universe I have made it, but now my dad will really know I’ve made it, because I’m doing a Super Bowl ad,” says Chenoweth, in an interview. “I had to say yes.” Likewise, says Sheen. “My 14-year-old daughter thinks it’s just the coolest thing in the whole world that her dad is in a Super Bowl commercial,” he says in an interview.  “A moment like that is really special.”

Advertisers spend months trying to figure out if they can match a celebrity with a particular concept – and asking consumers if the actor will affect the way they perceive the product they want to sell. Avocados from Mexico, says Luque, pre-tested several creative concepts and possible celebrity spokespeople before deciding.

Marketers often want a celebrity who will help tell their brand’s story, but not distract from it. In last year’ Super Bowl, Mars asked actor Danny DeVito to play a humanized version of its red M&M character, who is known to be a little excitable. “The ads to me that work the hardest are the ones where the celebrity is reinforcing the story,” says Miazga-Bedrick. “You can understand why that delivers more than working with a celebrity just to get the talk value.”

Celebrities often do their own kind of due diligence before deciding to take part. Olay wanted to make a commercial that highlighted women, knowing that they aren’t used in the lead role of Super Bowl ads as much as men. Gellar did a little research into the topic herself, she says, because “there is a responsibility that came with their commercial.” Chenoweth wanted to make certain the product was something could support. “I want to be proud of this,” she says. “I only put my name on things that I really believe in.”

And then there’s kismet. Sheen, who has done voice-over work for ads and appeared in commercials for DirecTV and Taco Bell, had no idea he would be appearing in Planters’ Super Bowl ad until a friend called him while the commercial was being shot.

“I was literally on aisle 9 in Gelson’s,” says Sheen, referring to the supermarket chain, when a friend told him producers wanted to swap out “a day player” if he’d take part. “I said, ‘Let me go home and shave,’” he recalls.

The appearance became even more fun when Sheen, who was supposed to be sitting on a bench while Mr. Peanut drove by furiously in a “Nutmobile”, got to change his one line. “The line was originally, ‘That guy’s driving like a nut,’” says Sheen. But with the actor, known for his controversial exit in 2011 from the hit CBS TV show “Two and a Half Men,” on set, executives saw an opportunity to try something else. The new line Sheen utters is, “And people think I’m nuts.” It went over well. “I could hear the immediate reaction. That was the keeper,” says Sheen. “It took it from being a drive-by into an actual moment,” he says. “It was a really good day.”

Sheen says he is focused on his health and family these days,  but hopes his appearance in the Planters ad might spark conversations about possible work he might do for others. “People are getting a really good version of me these days,” he says. “My days start at 4 a.m. They used to start winding down around that time.”

Movie and TV stars have to be prepared for the mechanics of commercial production. Every second counts and there’s little room for extended takes or adding nuance to character. “There is a different energy and a different type of acting,” says Sheen. “You just deliver and then you rely on their expertise, the creatives, the production team. They do it all day, every day, and so you are a guest in their arena.”

And actors must be prepared for the commercials to linger in popular culture. The ads often kick off campaigns that last for months, and sometimes get revived as artifacts of an earlier time when future Super Bowls take place. “This is an ad that will be airing all year for us,” says Miazga-Bedrick, the M&Ms executive. “It has to work hard for us. It’s not just one and done.” Chenoweth says she realizes being in the Avocados from Mexico commercial could make her “part of their history.”

Now the only thing left to do is watch the ads on Sunday night.  Chenoweth and Sheen are eager to do so. Gellar says she will be at the game at Mercedes-Benz stadium. In the middle of her interview, she learned her Olay commercial will appear on the venue’s Jumbotron screen while she is in the audience. Even for someone in the public eye, that’s something different. “That’s intimidating,” she says.