Now, with just a few days to go before stepping into the shoes of host Jay Leno on June 1, the comedian just wants to get started.
"I feel like a racehorse that was put in the stall five years ago and I feel now, like 'Let's go," O'Brien said on Tuesday.
"The biggest danger to me taking over 'The Tonight Show' is to overthink it. I think it just has to be a funny show...I think we are ready and we have a lot of fun stuff planned," he told reporters in a conference call.
O'Brien, 46, wrapped up his last stint of 'Late Night with Conan O'Brien' in February, and moved his family and crew to Los Angeles from New York.
Next week, as part of a major reshuffle on the fourth-ranked NBC network, O'Brien takes over from Leno on 'The Tonight Show.' Leno will move to an earlier prime-time spot in the fall with a week-night comedy show.
O'Brien, a former writer for 'Saturday Night Live' and 'The Simpsons,' said his first-week guests will include actors Will Ferrell, Tom Hanks and Gwyneth Paltrow, and "American Idol" host Ryan Seacrest.
O'Brien said audiences should expect more visual and sketch-like comedy than the stand-up routines perfected by Leno in his past 17 years behind the 'Tonight' desk.
"Jay's real love is the jokes. I come more from a sketch background and try to visualize what would look funny," he said.
"My true joy has always been to put a flashlight under my chin and predict the future...I like being silly," he said.
(Reporting by Jill Serjeant)
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