Before Tropic Thunder opened, the trailer had been playing in theaters (and on laptops everywhere) for seemingly forever. The very funny -- and often razor-sharp -- big-budget film about the ridiculousness of big-budget films lampoons just about everything under the Hollywood sun. Per the previews, you probably know that Ben Stiller plays a fading action star; Jack Black, a tubby Warhol-wigged comedian; and Robert Downey Jr., an Australian method actor who undergoes an experimental pigmentation procedure in order to play an African-American soldier. All three are thrown together on the set of yet another Vietnam War picture (cue CSNY and the majestic helicopters!), where Steve Coogan is their bedraggled director.

But besides a high-powered cast, the movie had a secret, too, which Paramount and DreamWorks did their best to keep under wraps until after the film opened: that a small, uncredited performance from Tom Cruise steals the whole show. In Tropic Thunder, Cruise plays Les Grossman, a bald, hirsute, foul-mouthed studio mogul with a penchant for hip-hop hip-swiveling moves. It's an astonishingly funny and surprising supporting performance (especially considering Cruise's last outing was in the dreadful, if well-meaning, Lions for Lambs). But producers have been trying to keep it quiet, playing up in photos the outrageousness of Downey Jr.'s blackface and Stiller's ever expanding biceps.

In fact, when set shots of Cruise dressed in character surfaced on the Web in November of 2007, his lawyers (who seemingly have work to do all the time) threatened action, and the photos quickly disappeared. (Google it, though; some have crept back.) No one involved in the production -- not Stiller or his co-writers, Justin Theroux and Etan Cohen, nor the producers or co-stars -- had been willing to talk about Cruise's performance until after the film was in theaters. Cruise's past directors wouldn't even talk. (It was a lockdown!) But we'll say it: Once again, Tom Cruise has managed to completely flip our perceptions of him upside down and inside out. It doesn't spoil a thing to say that the film is worth seeing for Cruise's performance alone, or that we hope this might usher in a new era for the strange, secretive actor. Could it be that, in fact, Tom Cruise actually gets it? Is it possible that Tom Cruise has a sense of humor about being Tom Cruise? Can we love him again without also feeling creeped out?

Of course, this isn't the first time we've reassessed Tom Cruise. In 1999, 18 years into a career that had him as the go-to American leading man, with those gleaming giant teeth, he surprised audiences with his turn as Frank TJ Mackey in Magnolia, a cold, coiled mass of furious energy, whose first three words in the film set the tone for his character: "Respect the cock." Critics raved, and Cruise received an Academy Award nomination (his only other nominations came from 1996's Jerry Maguire and 1989's Born on the Fourth of July). In one supporting role, Cruise added a whole new layer to his image; he could do big box office, he could do political, and he could also do weird and indie.

But the last almost-decade has been bumpy for the 46-year-old superstar: Big blockbuster turns in movies like the Mission: Impossible franchise and War of the Worlds and an almost too convincing portrayal of a sociopath in Collateral have been overshadowed by the very public perception of the private life of Tom Cruise: the A-list divorce; the salacious tidbits on his deepening faith with the controversial Church of Scientology and the recruiting videos that made their way to the Internet; the marriage to that young Dawson's Creek gal; the infamous Oprah appearance; the Brooke Shields fight; and the contentious Matt Lauer interview on Today. Things seemed to come to a head in the summer of 2006, after endless bad press, when there was a public fallout with Viacom's chairman, Sumner Redstone, who sent a fairly clear message when he told The Wall Street Journal that it was the superstar's erratic behavior that led to his and Viacom's ending of the long-standing relationship with Cruise/Wagner productions. "As much as we like him personally, we thought it was wrong to renew his deal. His recent conduct has not been acceptable to Paramount," he said. It wasn't quite a public relations meltdown of the Britney Spears level, but it must have smarted for a man who had consistently been described as the consummate professional and an intense perfectionist.

Ben Stiller seems an unlikely savior. But according to an article in Men's Vogue penned by Cruise, when the two men were introduced in 1992 by the actress Jeanne Tripplehorn on the set of The Firm, they hit it off immediately. ("We shared common ground in a love of cinema and a desire to tell stories and challenge ourselves and develop as artists," writes Cruise.) In 2000, the pair joined up for the hilarious short-film spoof Mission: Improbable, which aired on MTV, in which Stiller plays Tom Crooze, Cruise's supposed stuntman (funnily enough, The New York Times ended up using that very same pun as a headline for an article about Cruise's business moves in 2007). Cruise has already signed on to work again with Stiller, this time as a co-star on The Hardy Men, due out sometime next year.

Could this be an era of a friendlier, gentler, funnier, less scarily intense Cruise? Or is it just another career calculation for a tightly controlled and disciplined star who has managed to stay on the top for over a quarter of a century, and to make films that have grossed over a billion dollars? Reportedly, the actor has instructed his CAA agents to seek out funnier scripts for him, and he's taken more than one meeting with the ever-prolific Judd Apatow. ("He's quietly one of the great comedic actors in the country," Mr. Apatow told Entertainment Weekly in 2006.)

Whatever the motives, his performance in Tropic Thunder is sure to cause a stir similar to that of Magnolia. (What is it that makes it seem so wrong to hear him curse like a longshoreman?) He uses that thousand-yard stare to hilarious effect -- and just wait till you see his dance moves. "The first thing I thought of with the character of studio mogul Les Grossman was that I wanted him to dance," Cruise wrote in his article. "I have no idea why. When you have these impulses, you're not sure if it's a good idea or maybe the worst idea in the world."

Of course, Cruise was savvy enough to know that industry tongues would wag over him playing a crude and lewd studio head for Paramount Pictures; before the first industry screening of Tropic Thunder in April, he made sure to have a public bury-the-hatchet lunch with Redstone. At that early screening, Cruise's performance apparently brought down the house. Of course, Hollywood loves nothing more than to examine its own sickly white underbelly. But perhaps what they were also responding to, as they watch this typically steely figure don makeup, a prosthetic belly and do the bump and grind, is that Tom Cruise has managed to surprise us again. This time, thankfully, it's in a good way.

This story first appeared in the New York Observer.