Letterman Warms Up to Kick Off His Really Big ‘Shew’ : Television: Jay Leno drops in as rehearsals get under way at the new CBS ‘Late Show’ site: the old Ed Sullivan Theatre.

The executive producers of “The Late Show with David Letterman” had a surprise visitor recently: Jay Leno. Leno, in town for a publicity photo shoot, decided to drop in on the Letterman show at its new digs, the Ed Sullivan Theatre on Broadway.

“When they buzzed me that Jay was here, I rushed around the office putting the names of some phony guests--Madonna, Frank Sinatra (two songs)--on the wall,” said executive producer Robert Morton, referring to a Post-It chart of possible guests in his office. “I walked into (fellow executive producer) Peter Lassally’s office, saying, ‘We’ve got Jackie O.’ Jay said, ‘Very funny. And we’ve got John Kennedy Jr.’ ”

The two sides, who have known each other for years, wished each other good luck. (Letterman himself was not present.) But, come Monday night, when the new Letterman show premieres, they will be mano a mano in the long-awaited late-night sweepstakes.

On Thursday morning workmen were still finishing up the show’s set below the Gothic arches of the Ed Sullivan Theatre, a 60-year-old former Broadway house in which the ghosts of Elvis Presley and the mop-top Beatles hang over the stage where Sullivan introduced his “really big shew” in the 1960s.

Although Morton said that the format of Letterman’s new show will remain essentially the same as his NBC program, he acknowledged there will be more of an emphasis on celebrity guests. Bill Murray and Billy Joel will be guests on Letterman’s premiere night (Leno has Luke Perry and Garth Brooks booked against them), with Robin Williams, Debra Winger and the music group Soul Asylum also booked for the first week. Guests for the second week, Morton said, will include Vice President Al Gore, Michael J. Fox and comedian Steven Wright.

“We can’t have Bill Murray and Billy Joel every night, but we know that a lot of people will be especially tuning in during the first few weeks, so we didn’t want to have just Kamaar the Magician on,” said Morton, referring to the frequent Letterman guest who messes up his magic tricks.

Letterman, whose studios were housed in the network’s Rockefeller Center headquarters, will no longer have the NBC management--or NBC talent--in the same building to kick around any more. But the Ed Sullivan Theatre is only a few blocks away from both CBS’ corporate headquarters and the studios of CBS News, and Letterman will continue to do “remotes” from around the city. (A recent one involved a segment called “Ask Zsa Zsa,” in which Letterman traveled to the suburbs with Zsa Zsa Gabor, asking startled homeowners if they had a question for Ms. Gabor.)

Some of the people who wrote for tickets to the Letterman show were surprised to find that their tickets were for dress rehearsals this week. The two dress rehearsals--with comedians David Brenner and Martin Mull lending a hand--may or may not air later on, Morton said. They were designed to allow Letterman to get a feel for the theater and work in front of an audience after a two-month hiatus. Letterman joked on-stage that one of the reasons he likes CBS is that CBS owner Laurence Tisch “lets me call him Daddy.”

The theater, which CBS bought for $4 million before refurbishing, houses 400 people--and may offer some comedy possibilities for the Letterman staff. One dubious benefit of the site so far is the strong smell of chicken frying that emanates from a restaurant below. CBS sent over an environmental expert to try to figure out how to get rid of the smell--and the producers videotaped the man as he checked out the vents in the theater.