Box-office stars Tom Cruise and Adam Sandler both stepped out of their comfort zones in movies that opened this weekend — “Rock of Ages” and “That’s My Boy” — and landed flat-footed.

Warner Bros.' $74-million "Rock of Ages," with Cruise as an aging rock icon, opened to a disappointing $15 million. Sony's $65 million "That's My Boy," with Sandler in his first R-rated comedy, did even worse with just $13 million.

Both are likely to lose money, say box office analysts.

To put it in perspective, the grosses of “Rock of Ages” and “That’s My Boy” combined couldn't match "Madagascar 3," an animated film in its second week, which took in $35 million.

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That’s bad news in a summer when other movies with reliable stars – Johnny Depp in “Dark Shadows” and Sacha Baron Cohen in “The Dictator” — have had less than successful theatrical runs.

The movie stars in “Rock of Ages” didn’t seem to help much. Despite the presence of Cruise, Alec Baldwin and Russell Brand, “Rock of Ages” did no better its opening weekend than last year’s “Footloose,” which had no stars to speak of.

The weak results add to a roller-coaster summer marked by a handful of successes and lots of collateral carnage that even reliable movie stars can't seem to escape.

For Cruise, whose movies have made more than $3 billion at the box office, and Sandler, whose films have made $2 billion, the numbers are a major comedown.

"Tom Cruise today doesn't open a movie anymore unless it's a certain type of film, like 'Ghost Protocol,'" said an executive at a rival studio, "and this wasn't it." Cruise's last film, "Mission: Impossible – Ghost Protocol" opened to $30 million and made $693 million worldwide.

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In the case of “Rock of Ages,” exit polls indicated that young people just didn’t show up. The audience, which gave the film a B CinemaScore, was 62 percent female, and 74 percent were over 25 years of age.

To be fair, Cruise was not meant to draw the young women. Executives close to the film said that Julianne Hough, still something of an unknown, and the campy comedy of Brand and Baldwin were supposed to draw that audience, who – it was hoped – would bring their dates. That didn’t happen.

"Just about everyone I spoke to who has seen the movie loved it," the executive at the rival studio said, "but then, just about all of them were between 30 and 40 years old.”

Much of the marketing materials were built around Cruise, though TV commercials played up music from Poison and Twisted Sister, one analyst noted.

There were reasons each failed to connect, but one of the simplest may have been bad timing. Father's Day, with its brunches and the NBA Playoffs and U.S. Open golf on TV, no doubt cut into their male audiences.

For Sandler, "That's My Boy" is a genuine pratfall, his second in a row coming on the heels of last year's "Jack and Jill." (And even "Jack and Jill" opened to $25 million.)

"Audiences expect certain types of films from certain actors, and that's definitely the case with Adam Sandler," said an executive from another movie studio. "This wasn't it."

The comedian’s first R-rated comedy drew an audience that was 54 percent male and 52 percent under 25, the latter number suggesting that the rating may have cost it some young moviegoers.

Going the R-rated route, in theory to connect with his aging audience, seems to have hurt rather than helped. "His audience is aging," said the executive, "and they've had kids, and they want to go with their kids to see an Adam Sandler movie."

Meanwhile, director Adam Shankman and his sister-producer Jennifer Gibgot, who run Offspring Entertainment and produced "Rock of Ages," said in interviews they were hoping young men would go for the hard rock theme.

"This is 'Mamma Mia' for dudes," Gibgot quoted Shankman as saying in an interview last week.

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One marketing executive didn’t see the logic: "It's a musical, you've got Alec Baldwin running around in weird hair and it's filled with songs from the 1980s," he said. "How many young guys want to see that?"

Because the film is such a departure from his action spy roles, Cruise isn't likely to be hurt by this going forward. Paramount and most observers remain bullish on the upcoming "Jack Reacher," with its built-in Tom Clancy fan base. It opens Dec. 21.

The "Rock of Ages" misfire may be creating some consternation at Universal, though. That studio bows its own big-budget star-studded musical "Les Miserables" on Dec. 14.