The rise of the R-rated preview.

Universal is now back in the game, making red-band trailers for movies like Wantedand Forgetting Sarah Marshall. That's partly because a major exhibitor—Regal Entertainment Group, which operates the most movie screens of any company in the United States—decided in March to allow restricted trailers on its screens. But Regal's decision is more a symptom than a cause of the red-band renaissance. While it's still rare to see a red-band trailer in a brick-and-mortar theater, you can fire up a couple of dozen on the Web any time you want. The MPAA mandates that online red bands must be restricted to sites that cater to an adult audience or be kept behind some kind of age-verification wall. Even so, most red-band adverts are easy to find on YouTube—at least until the Federal Trade Commission decides it's time to issue another 116-page report. (The MPAA has created an in-between trailer category, the yellow band, that's designed for "age-appropriate Internet users." It hasn't really caught on yet—only six or so have been made in the last 18 months—and probably won't, considering how easy it is to find the more salacious red bands.)

Given the popularity of movie trailers on the Web, the potential audience for a red-band preview has gone from minuscule in the Showgirls era to virtually limitless in the time of Pineapple Express and Zack and Miri. Compared with an R-rated trailer that's screened in theaters, a Web-based red band is more likely to get talked up and to reach a target audience of (possibly under-17) fan boys who'll line up for a screening on opening weekend.

Along with doing heavy lifting as a viral marketing tool, red bands can also give potential viewers a better sense of what's in the movie. Pekurovskaya, who has done publicity for Judd Apatow in recent years, says the red band is the perfect medium to display the auteur's unique style. "On the Judd films, they are the juxtaposition of the really raunchy with the very sweet," she says, "and when you can only show half of that equation, you're actually misrepresenting his films. … You're doing a bit of a disservice to the audience."

The studios are still learning to deal with the relative lassitude of the restricted-trailer art form. Considering the red band's restrictions on "excessive sex or violence," trailer-makers have the most room to play with language. The red-band trailer for the Coen Brothers' Burn After Reading, for example, does little more than restore a few shits and a dickwad that were cut from the all-audiences version.

Despite those minimal alterations, that Burn After Reading trailer really works, showcasing the film's distinctive patter without using the trailer as an innuendo-enlarging funhouse mirror.

While a few extra shits never hurt anyone, there might be some value in holding stuff back. It's a long-held complaint that movie trailers give away too much—that marketers dump all the best lines into the preview, enticing people to spend $10.50 to sit through a movie that's already been strip-mined for its richest material. R-rated trailers exacerbate that problem by revealing swaths of the movie that were previously untrailerable.

Compare the red-band trailer for Superbad with the green-band one. The R-rated version includes the lines "I am truly jealous you got to suck on those tits when you were a baby," "the funny thing about my back is, is that it's located on my cock," and "I arrested a man-lady who was legally named Fuck." The all-audiences trailer has none of that material, relying on well-placed cleavage and quick, pre-swear-word cutting to suggest the movie's saltier material. The red-band trailer is probably more likely to get teenagers to buy a ticket for opening weekend; it's also a better indication of what Superbad is all about. But perhaps the movie would be more enjoyable if you'd seen less of it beforehand.

Correction, Sept. 22, 2008: Due to a copy editing error, this article misquoted a line from the trailer for Zack and Miri Make a Porno. In the trailer, Rogen's character says he would like to watch "a tape of Rosie O'Donnell getting fucked stupid." (Return  to the corrected sentence.)