Junket ['jun-ket] n 1: A promotional event prior to the release of a motion picture during which the stars and filmmakers sit in hotel rooms for several days while hundreds of journalists from all media interview them. 2: Fear Factor, showbiz-style

''It's factory work.'' That's how Julia Roberts, on the set of America's Sweethearts, disarmingly describes the Kafkaesque-death-march-with-stale-Danish known as the movie junket. ''I mean, the last one that I did, I worked the full week [filming Sweethearts] and then did the Saturday-Sunday junket [for The Mexican]. Sunday night I flew to New York, did press all day Monday, flew back to Los Angeles, and worked Tuesday, Wednesday, Thursday, Friday. By Saturday, my mom could have called, and I would have said, 'Your name again?' ''

Given that attitude, it's fair to wonder: Why is Roberts so sanguine about starring in a romantic comedy set in that very world? Maybe because she's not playing the star. In fact, her role as the dowdy sister/assistant to a big-screen diva (Catherine Zeta-Jones) allows Roberts to attend the junket within the film as (insert deep sigh of relief here) a bystander. ''I sat in a chair on the side of the room, and I knitted and took water over,'' she says. ''You know, 'Do you need a cappuccino?' I was like, 'This is the best junket EVER.' ''

Then again, there's a delirious through-the-looking-glass quality to almost everything about America's Sweethearts. When the $46 million comedy hits theaters July 20, it will mark the first top-drawer release from former Disney head Joe Roth's production company, Revolution Studios (following the low-budget, lowbrow comedies Tomcats and The Animal). Not to mention that for his first directorial effort in 12 years, Roth has chosen a project that mischievously presents a portrait of the Hollywood machine in full-on nervous breakdown.

The movie imagines that the national press has been flown to a rococo Las Vegas hotel for a screening of a new romantic thriller called Time Over Time (''He went back in time -- to save her future!''). But the screening isn't happening because, unknown to the assembled reporters, the movie's hippie-artiste director (Christopher Walken) has disappeared with the only print. The studio chief (Stanley Tucci) is freaking out, and the publicist (Billy Crystal, who also served as a producer and coscreenwriter of America's Sweethearts) must keep the media hordes at bay by hinting that the movie's married but now acrimoniously split stars, Eddie Thomas and Gwen Harrison (John Cusack and Zeta-Jones), are reconciling. Complicating matters, Eddie seems to be falling in love with Kiki (Roberts), Gwen's newly slim mouseburger of a sister.

And that's just in the MOVIE. We haven't even begun to address the life-imitating-art-imitating-life weirdness of a film about a celebrity uncoupling arriving right at the moment when Roberts splits with Benjamin Bratt, her boyfriend of nearly four years. Or the nasty felicity of an inside-the-PR-maelstrom comedy being distributed by Sony, the studio recently busted for creating a fictitious critic to provide positive quotes for some movie ads and for drafting employees to provide man-on-the-street testimonials for a Patriot TV spot.