Jonathan Elsner, 11 years old, has seen both Ace Venturas; The Mask; Dumb & Dumber; Batman Forever; and Liar Liar. Loved them, in fact. Now Jonathan is flying from New York to Los Angeles for a bar mitzvah. The in-flight coming attractions show a trailer for Jim Carrey’s new movie, The Truman Show. Jonathan glances up from his Game Boy to watch. I tell Jonathan I will be interviewing Carrey tomorrow, and he says there’s one thing he’s curious about.

“What’s Jim Carrey really like?”

That question is why I’m on this airplane. In The Truman Show, Carrey plays Truman Burbank, the only “real” person in a 30-year live television soap opera (Tru-man -- get it?). One-point-seven billion viewers “know” Truman -- they’ve watched his every move, from birth to puberty to marriage to bathroom routine, courtesy of 5,000 hidden cameras. Truman is unaware that he’s being fed live to a satellite, and that everything in his life is a fake -- his parents are actors, his hometown is a stage set. Famous around the world, Truman doesn’t know himself. Hey -- kind of like Jim Carrey, prey of the paparazzi, seeker of spiritual connection.

The Truman Show is that rare mainstream movie, like Easy Rider, Network, or Thelma & Louise, that is perfectly timed with the Zeitgeist. O.J. and Princess Diana have elevated the all-consuming, invasive celebrity spectacle to a new and queasy level. Jerry Springer has stoked the debate about voyeurism and the packaging of human emotion. Technology is obliterating privacy: Today you were videotaped at the ATM, your e-mails were permanently stored in the corporate mainframe, and Amazon.com is sifting your reading tendencies and recommending more books for you to buy.

Scarier still is the rabid globalization of the media-industrial complex. We are becoming one world under Rupert Murdoch, with a single subject of pop-culture conversation beamed into homes from Beijing to Baton Rouge. Titanic -- based on a true story! -- washes into Monica, who exits for Seinfeld, who shuts down just in time for Sinatra. “Cool hunters” ferret out any hint of an underground for their retail sponsors, so that today’s rebellion is sold as next season’s smart-priced fashion trend. Every emotion is commodified.

The Truman Show, besides being fun to watch, deftly comments on this late-nineties blurring of life and entertainment. And Carrey -- a wild exhibitionist onscreen, a star instantly recognizable to millions, a man with no privacy -- seems seductively positioned to bring his real life to bear on the role.

“Truman Burbank is a kind of hothouse flower,” says the film’s producer, Scott Rudin. “He’s been raised under glass. And Jim has the quality of having been created. He doesn’t seem like a regular person who grows up in a regular house.”

Jonathan Elsner has another important question: “Did any of those animals in Ace ever take a bite out of him?”

The dead man is live on every channel. After landing in Los Angeles on a hazy-gray Thursday afternoon, I drive to my hotel on Sunset Boulevard and, out of habit, flip on the TV. There’s a view from a hovering news helicopter -- actually, slightly different views of the same scene from multiple helicopters. Offscreen anchorpeople bring us up to date: A man stopped his pickup truck in a freeway car-pool lane. For more than an hour, this man has raged, by cell phone, to the police about his treatment by an HMO. He’s mentioned Molotov cocktails, his dog, and a shotgun.

Videotaped flashbacks show us the man emerging to unfurl a banner and lay it flat along the highway, the better to be read by the overhead cameras. Another replay shows the man leaping out of the pickup truck as it bursts into flames, peeling off his burning clothes, then reaching into the back of the truck for a shotgun. He carries the gun over to a low dividing wall, braces it against the concrete, and puts the barrel in his mouth.

“Is that the best angle you have?” says the guy on Channel 7. “He’s down, but we can’t see much at this distance.”

At this moment, Jim Carrey is riding in the back of a limousine. He had returned by private plane to Los Angeles after several days in Montana, where he’d been working on the screenplay for a remake of a Don Knotts movie and hiding from the paparazzi. Now Carrey is coming home to generate some carefully controlled hype for The Truman Show.

Carrey is listening to the limousine radio as callers chatter about L.A.’s first live televised suicide. “I was just amazed,” he says the next day, “at how many people were calling in and saying, ‘Man, I can’t wait to see it again!’ It’s very strange. I don’t understand it.”

The suicide couldn’t be better timed for Truman, however; Carrey and the movie’s other principals mention it so often you begin to wonder if the shooting was staged for their marketing campaign.

Carrey arrives at Smashbox, a gleamingly hip photo studio hidden among the scrubby warehouses of Culver City, looking like a mild-mannered guitarist for a rockabilly band. His brown hair, grown to nearly shoulder length, is slicked back, and long sideburns snake down his cheeks. A dark-green shirt flaps untucked over Carrey’s basic blue Levi’s. Carrey is more handsome than he’s ever appeared in a movie. The nasal honk of his Canadian accent is more pronounced, as well. There is an immediate naïveté and vulnerability about him.

Carrey is trying hard not to be funny. His eyes light up when he hears a big fat straight line, but instead of flapping his long arms or contorting his rubbery face or spewing out a twisted punch line from his random-access brain, he stuffs the joke genie, forcibly, back into the bottle.

Blame it on The Cable Guy. Carrey is obsessed with the idea that the 1996 movie, for which he was paid a record-setting $20 million, was perceived as a failure not because it was leaden and mean-spirited but because the marketing was all wrong. “The studio played up the sillier stuff, to get people in the first weekend,” he says. “And I’m not gonna make the same mistake twice.” Years ago, Carrey’s agent and co-managers mapped out a strategy to build Tom Hanks-like respect and longevity for their client, by alternating dramas and comedies. Truman is a key test of that agenda.

A cushy green couch is available, but Carrey coils atop a spindly straight-backed chair that’s too meager for his elongated frame. He looks like a giraffe trying to get comfortable on a barstool. Even as Carrey holds himself in, determinedly restrained and normal, he comes across as somewhat freakish, otherworldly.