Conan O'Brien Conan O'Brien

Show minus stars equals different show: It's one of the mantras of Jump the Shark, and it's true — unless, maybe, the show is The Tonight Show.

The Tonight Show is an institution that has had only four full-time hosts in more than half a century. Jack Paar, Steve Allen, Johnny Carson and Jay Leno all made their own imprints on the show, but in the way a minister does a church. Whether or not congregants like his or her personality or jokes, the basic religion stays the same.

Leno is the genial, gently ruthless host of the ultimate gossip mill, whether persuading Hugh Grant to open up about his dalliance with a hooker, breaking the news of Arnold Schwarzenegger's run for California governor, or, this week, getting Mel Gibson to confide that he'll soon be a dad again. A standup at heart, Leno thrives on current events.

Carson was the suave host of the best cocktail party in the country — one where everyone was welcome — who sometimes ended the night with a lampshade on his head. Ever polite, he made all of his guests seem interesting, and was a master of the kind of timeless, slightly risqué joke that would play from here to vaudeville. (When his Art Fern character explained that early to bed and early to rise makes a man healthy, wealthy and wise, a buxom sidekick asked if going to bed would make her wise, as well. "No," he said. "But it'll make you wealthy." This was in 1989.)

Paar, who made the show the institution it's become, was a golden-voiced conversationalist more interested in witty dialogue and thought-provoking exchange than punch lines. Shy off-stage, he was unpredictable on, especially when he announced, on-air in 1960, that he was quitting because of a censored joke. He said there had to be a better way of making a living, but soon returned — saying he had looked and there wasn't.

Steve Allen was the first host of the show, and gave it elements that last to this day. Leno's "Jay Walking" segments owe a debt to Allen's man-on-the-street interviews, and the man practically invented audience-participation skits. Plus, one of his first guests was a young comedian named Johnny Carson.

Whoever hosts, the Tonight Show has always been one of the most happening places on television: a place for the hottest stars to promote the biggest movies, shows and music. It's also a place for young talent like Leno, David Letterman, and once, even Carson to break out. Occasionally it's even a place for big ideas and earthshaking political announcements.

Do you think any of that will change with Conan O'Brien manning the Tonight Show desk?

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