With several TV columnists predicting that he is likely to become the biggest beneficiary of NBC's decision to remove Jay Leno as host of the Tonight show and replace him with Jimmy Fallon, David Letterman seemed to be in particularly fine fettle Wednesday night. He opened his monologue by remarking, I got a call from my mom today, she says, 'Well, David, I see you didn't get the Tonight show again.' As the laughter subsided, he continued, NBC, God bless 'em, announced the official date for Jay Leno's departure -- no mention of his official date of return, however. It was, of course, a reference to NBC's decision to replace Leno with Conan O'Brien in 2009 and then bring him back as host of Tonight eight months later. Didn't we just go through this? he asked the audience. I mean, it's crazy. He's being replaced by a younger late-night talk show host -- what could possibly go wrong? Honestly. They had pretty good luck with this in the past. Letterman was even on Leno's mind as he opened the Tonight show with this similar riff: I had a really awkward day today. I had to call David Letterman and tell him he didn't get the Tonight show again. As for NBC's strategy of courting younger late-night viewers, Leno quipped, NBC says in five years they plan to replace Jimmy [Fallon] with Justin Bieber. Fallon appeared unable, or unwilling, to milk Tuesday's announcement for jokes, but he did appear to reveal when the transition will take place -- and it won't be next spring, as the official announcement on Wednesday had indicated. I'm going to be taking over the Tonight show next February, he said, but don't worry. Until February our focus is right here on whatever this show is called. In an interview with today's (Thursday) New York Times, Leno indicated that it was he who suggested the February changeover, pointing out that it would give the network a chance to promote Fallon during the Winter Olympics. Over at TBS, Conan O'Brien barely mentioned the matter, merely congratulating Jimmy Fallon and not saying a word about Leno. He's going to do a fantastic job, O'Brien said of Fallon. Likewise, at ABC Jimmy Kimmel congratulated Fallon, referring to him as a formidable rival and an incredible lover. Meanwhile, Leno told the Times that he plans to continue appearing at comedy clubs and The Like, but has no plans to return to late-night television. Not that he wouldn't like to return, he indicated. Would I do it again? Believe me, the phone's not ringing off the hook. It will be nice if people seem interested.