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?...