Even before The Tonight Show began, O'Brien joked in a promo: "It's an amazing show, airing who knows when?"
He got a long, rousing round of applause when he walked out to start the show and tried to quell the crowd by wisecracking: "Ladies and gentlemen, please. You keep that up and this monologue won't start until 12:05. And then where would we be?"
He continued: "Good evening, everybody. I'm Conan O'Brien, the new host of Last Call with Carson Daly."
He went into a joke about an earthquake that hit California and "was so powerful it knocked Jay Leno's show from 10 o'clock to 11:35."
"Everybody wants to know what my plans are," O'Brien continued. "Everyone's asking me. All I can say is I plan to keep putting on a great show night after night while stealing as many office supplies as humanly possible. I'm going to rob this place blind. I got 10 cartridges of toner shoved in my pants right now — just jammed down there." (Watch more of the monologue)
He also joked that a report that NBC anticipates losing $200 million on its 2010 Olympics coverage was "hilarious," and suggested he may "leave television altogether and work in a classier business with better people, like hard-core porn."
Leno wasted no time in jabbing NBC earlier, beginning: "As you know, we're not just a show anymore, we are now a collector's item."
"Our show has been canceled. Fired again!" he exclaimed. (Watch the video)
To show how the network has "nothing" to air, he said, "Even when they fire people, it's a rerun. Didn't we just get fired in May?
"NBC said the [prime-time] show performed exactly as they expected it would, and then they canceled us," he went on. "When we were on late night, we performed better than expected, and they canceled us. That was totally different."
He said nothing was sure about the lineup shakeup and that NBC had managed to upset his and O'Brien's people. "NBC said they wanted drama at 10. Now they got it," said the host of The Jay Leno Show.
"I take pride in one thing: I leave NBC prime time the same way as I found it: a complete disaster."