This week, Evan Joe Millionaire Marriott and Trista The Bachelorette Rehn are getting more ink than Ben Affleck and J-Lo combined.

But they'd better enjoy their 15 minutes -- like the rest of the reality TV bunch, they have a slim chance of lasting Hollywood fame, say experts.

"Everybody is interested in these people when they first pop," says Hollywood casting agent Roger Mussenden, who helped Survivor cutie Colleen Haskell land a role in 2001's The Animal, with Rob Schneider.

"But so far, all of them have fizzled, even Colleen. I mean, where is she now?"

At the moment, neither Marriott nor Rehn can be blamed for thinking their stars will shine forever.

Rehn has a cameo -- wearing a wedding dress, of course -- on tomorrow night's episode of ABC's Less Than Perfect with Eric Roberts.

And casting agents have been sniffing around Marriott's hirsute chest, which is no surprise, given the more than 20 million fans who are expected to watch the final episode of Joe Millionaire on Fox tonight.

Marriott is even in the running to star in the new Warner Bros. Superman movie, which is scheduled to begin shooting in May and has already been turned down by Brendan Fraser, Jude Law, Josh Hartnett and Ashton Kutcher.

But Marriott shouldn't hold his breath on that -- or anything else.

"Joe Millionaire is a good-looking guy," Mussenden says. "But have you noticed what happens when he opens his mouth? It's like, whoa, please, don't speak."

To be a real star, you have to do more than eat a snake or propose to a near-stranger on live television.

"These people don't become real celebrities because they haven't done anything," says MSNBC gossip Jeannette Walls.

"These people are not like a Meg Ryan, that you think of as your best friend. Or Liz Taylor, who was always doing crazy things. Or Russell Crowe, the bad boy. Real celebrities occupy a place in our imaginations.

"The kind of fame these people have is like the fame that Monica Lewinsky and Donna Rice had. They're scandalous. The best they can hope for is to open a restaurant or a club. Maybe Joe Millionaire should do that."

As New York casting agent Jay Binder puts it, "They look like dopes, and after that, it's hard to see them as stars."

Almost all the Survivor vets who made the rounds in Hollywood after hitting it big have dropped out of sight.

Only former bartender Jerri Manthey is still on TV. She has parlayed her Survivor fame into another reality show, WB's The Surreal Life, which airs its final episode this Thursday.

Last year, Manthey rode a wave of fame just like the one Marriott is on. She got invited to all the parties and premieres.

"I was closer to people in show business than ever before," she says. "But after that, it slowed down."

So live it up while you can, Joe.

"These people are so well-known, they think they can come out to Hollywood and it will all open up to them," Manthey says. "But you'll get 20 doors slammed in your face before one person gives you a chance."