The host-to-be begins his run as Conan O'Brien's successor on March 2, and with just weeks to go, things are almost ready.
"The set is almost 90 percent there. I tried out chairs today and I sat behind my desk. It's all getting so real!" he said.
In fact, he said, the only preparations he's worried about are his own.
"I really hope it all goes well because I've got the best of everything around me and the only person that can screw it up is me. And I'm just really worried that I'm gonna screw it up," he said, noting that he's feeling more confident as the show date approaches. "Days are getting longer and I'm getting stronger."
O'Brien's final "Late Night" is Friday, February 20.
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