The elevators open on the sixth floor of 30 Rockefeller Center to reveal a hallway full of activity. We're hours away from another taping of NBC's Late Night with Conan O'Brien (not to mention test shows underway in an adjacent studio for Jimmy Fallon!). Three floors up on nine, where O'Brien and the writers work, however, the mood feels decidedly different. It's almost as if it's the last week of high school. Make that the funniest high school in America, and most of the students don't know how to react, because they're about to go on summer break in the spring, and meet up again in college in Los Angeles, where they'll put their own spin on The Tonight Show in June. How do you say goodbye, exactly?

The Letterman folks went through this all before in 1993, of course, when David Letterman jumped from 12:35 a.m. at NBC to 11:35 p.m. at CBS, providing the opening that O'Brien and his staff have more than ably filled.

Despite the high-school/college metaphors above, though, you don't get the sense that O'Brien's staff is suffering from a case of senioritis. It's just…different. Fewer guests to plan panel stories for, more clip packages to hunt down and edit, and a completely overhauled monologue for the final week. Out with the topical news and celebrity jokes, in with the goodbye quips. For Tuesday, writers prepared an elaborate farewell to the show's Masturbating Bear (played by writer Michael Gordon) that involved O'Brien trying to freeze him in carbonite in tribute to Han Solo, only to have Carrie Fisher herself rescue the bear and reunite with him after a chase through the streets of Manhattan.

Most clip packages got debated and selected months ago. On Wednesday, writers huddled in one of the offices trying to select clips for a last-minute addition to the highlight reels. Packages on Wednesday's show included a blooper reel of sketches gone awry, and a reel that showed how much they relied on robots, bears and Abraham Lincoln over the years.

Meanwhile, writers Brian Kiley and Guy Nicolucci are staring at their respective computer screens, racking their brains to come up with farewell one-liners for O'Brien's prepenultimate monologue. "Normally, you have a sense of what the good ones are and aren't," Kiley says of writing monologue jokes. He has known O'Brien since both attended the same Sunday School in a Boston-area Catholic church, and has a good feel for what kinds of topical jokes O'Brien likes to tell and which subjects to avoid. He'll go through the morning newspapers, find his marks, fact-check them, then type and email them over. For the final week, though, O'Brien just wants to use the monologue to say goodbye. One of Kiley's more TV-daring punchlines that made it onto the late-night airwaves Tuesday noted how you couldn't say the word "douchebag" on TV when Conan started in 1993. Nicolucci says it's like throwing jokes over a wall, waiting to hear which ones land and which ones don't. With an hour to go before the daily 4:45 p.m. meeting on the set with O'Brien, Kiley joins Nicolucci in his cramped office for some team brainstorming. Is there some way to still get a Paris Hilton mention into the monologue? Kiley offers: "We won't be on the air until June, so for the next three months, I'll be going door-to-door telling Paris Hilton jokes." Nicolucci exclaims, "Yes!" and types it up, quickly adding it to a lengthy e-mail correspondence.

They take a quick break to show me their putting skills. Nicolucci says his office used to be Andy Richter's, although when Richter had the space, it was much larger. When Nicolucci moved in, at one point, he had to share the office with two other writers. Cannot imagine that being fun at all.

At 3:50 p.m., Nathan Lane with award-winning composer Marc Shaiman on piano rehearse a tune Lane will sing for O'Brien on that night's show, in a throwback to the tune Shaiman composed for Bette Midler to sing to Johnny Carson for his TV farewell. The image of the Masturbating Bear makes Lane crack up. Take two. They rehearse this naughty ditty twice, both times without O'Brien on the set to ensure his initial reactions to it will be caught on camera that night. Apparently, Shaiman and Lane only began working on this themselves 10 days earlier. During the broadcast, Lane credits Shaiman and his partner Scott Wittman for the lyrics, which clearly show they have been paying attention to O'Brien's show over the past 16 years.

Nicolucci explains that you have to write a lot of jokes each day to find the few gems that make it on TV. ".150 is a good day. Here, if you bat .200, you're Ted Williams," he says. He and Kiley continue sounding out ideas. "In California, we'll have earthquakes," Nicolucci says. "He'll have to reinforce his hair," Kiley says. "Aha!" Nicolucci says, throwing his hands in the air, and then to the keyboard. "Things will be different in California. For instance, I'll have to get earthquake insurance for my hair." It doesn't make the cut on Wednesday.

After Friday's finale, the staff will come back to the office, pack up their belongings, and take some things home while leaving other posessions boxed up for NBC to ship out to their new digs at Universal Studios. Hollywood, here they come.

O'Brien's set on the sixth floor of 30 Rock, meanwhile, will get taken over by a new TV talked helmed by one of Oprah's doctors, Dr. Oz. I suppose that's a good transition as any, as for many years, this studio proved that laughter indeed was the best medicine.

Related reading: The New York Times checks in with Conan.