Jay Leno, Conan O'Brien, Jimmy Kimmel and Jon Stewart all return to late-night television this week, but aside from their familiar faces, viewers may not recognize much.

David Letterman is also returning to the air — but with a deal allowing him to use his writers again.

Robin Williams will be Letterman's first guest upon the return of his "Late Show" on CBS tomorrow. The appearance of a Hollywood A-lister who can talk a mile a minute may be Letterman's way of quickly trying to draw a distinction between his show and his late-night rivals, who are without writers and may also have trouble booking major entertainers as guests.

Letterman announced Friday that his production company, Worldwide Pants, had reached an agreement to have his show return with writers despite the continuing writers strike, which began Nov. 5. The deal also allows writers to return to Craig Ferguson's late-night show, also owned by Worldwide Pants.

NBC said Monday that Republican presidential hopeful Mike Huckabee will appear on Jay Leno's returning "Tonight" show tomorrow.

Late-night shows hosted by Kimmel and O'Brien are also returning tomorrow, but have said little about who will be appearing. Jon Stewart and Stephen Colbert come back to Comedy Central on Monday. Barring a New Year's miracle, none of their writers will be joining them.

The hosts — with the exception of NBC's Carson Daly — are also members of the striking Writer's Guild of America, making them subject to union rules that would severely limit what they can do.

The union's strike rules say members cannot write or perform any material that would normally be written for them. Under this interpretation, for example, Jay Leno couldn't perform a monologue, because his staff of writers normally crafts his jokes. The comic skits that are a part of several late-night shows would also be off-limits without writers.

"I think that people will see some interesting television," said Chris Albers, former president of Writer's Guild of America East and a comedy writer for O'Brien. "Obviously, these are some of the funniest people in the country so they're probably going to do a very good job. It's just a different animal than what they're used to and what we're used to."

In a conference call with reporters last week, producers of NBC's "Tonight" and "Late Night" said they were still trying to figure out what their shows would look like.

Comic ad-libbing, musical performances and lengthier appearances by interview subjects willing to cross picket lines are the most likely recourse.

"I don't know what they're going to do," said Mike Sweeney, head writer for O'Brien's NBC show. "My obvious speculation would be more guests, and maybe talk to them more slowly."

Sweeney has his own secret wish for O'Brien, as he returns without writers.

"I hope he tries to hold a telethon to raise money for us," he said.

Stewart and Stephen Colbert would appear to have the toughest time reconfiguring their programs, which have a large amount of scripted material. By a strict interpretation of the guild's rules, a member would be prohibited from performing as a character if union writers normally write material for the character.

Colbert performs his entire show in the character of a blowhard political commentator.

"We don't know how he's going to do it," said Sherry Goldman, spokeswoman for the Writers Guild of America East, "and I'm not so sure that he's figured it out yet."

Comedy Central would not let its executives talk about planning for the shows' returns.

Only two late-night shows were affected when writers went on strike in 1988: Johnny Carson's "Tonight" show and Letterman's program, both on NBC. Carson was not a writer's guild member, so he wrote his monologue himself for the few weeks that he worked without writers.

His monologue, part of the fabric of American life, was welcomed back, but Carson's writer-less debut in May 1988 didn't draw raves.

"The whole show seemed lame," wrote the Washington Post's Tom Shales at the time, "unfunny comic Joe Piscopo, Ed McMahon showing photos of his little girl, a hackneyed arrangement of Irving Berlin tunes by the band and film of mating condors."

Letterman's "Late Night" substituted comedy with freewheeling filler. One gag had the show's associate director playing "Lady of Spain" on the accordion, night after night.

"Fifty-five minutes, ladies and gentlemen, 55 minutes to go!" he said early in one show. "That's all we're really trying to accomplish, is to eat up valuable network time."

Letterman weighed in frequently on the strike, calling network management "money-grubbing scum."

While the strike raises the possibility of train-wreck television, some performers may thrive in without-a-net circumstances.

A critic in The New York Times wrote that Letterman's strike programs were often "downright exciting," a throwback to the early years of late-night television when there was more improvisation.

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