Conan O'Brien made his "Tonight Show" debut Monday -- but critics weren't exactly roaring with laughter.

"After one show, let's say he's a work in progress," wrote Randee Dawn of The Hollywood Reporter. "O'Brien commanded the stage, but seemed more comfortable laughing it up with erstwhile sidekick-turned-announcer Andy Richter than in interacting with his 380 audience members."

O'Brien's opening monologue mostly consisted of "sketch upon sketch" -- notes New York Post TV critic Linda Stasi -- most of which were "at times, painfully unfunny."

In one scene, O'Brien -- who spent the last 17 years as host of NBC's "Late Night" -- was shown jogging across the country from New York to Los Angeles. "I think I've timed this move perfectly," he quipped. "I'm on a last-place network, I moved to a state that's bankrupt and "The Tonight Show" is sponsored by General Motors."

Other clips showed him giving a tram tour of Universal Studios, sitting in the last row of a Lakers game (to show how well he's acclimated to L.A.) and paying homage to his beat-up 1992 Ford Taurus.

"Again," said Stasi, "not a million big laughs."

David Hinckley of New York's Daily News said the bits "lasted too long." Said Hinckley, "He's from the world of sketch comedy, not monologues, and he sticks with an idea as long as he feels something funny could happen."

Ken Tucker of Entertainment Weekly got a chuckle out of the sketches.

"All in all, a large-scale, impressive debut," he wrote. "But we all know that success in late-night depends on the long haul -- Conan knows this as well as anyone. So now I want to see how he follows up his glitzy debut."

Added USA Today's Robert Bianco: "Overall, the show wasn't O'Brien at his funniest, but it was funny enough to get by."

David Letterman definitely took notice of his new competition.

"I'm still here," Mr. Letterman told his audience on his show Monday night. "I knocked off another competitor."

He said that his mother had called him to say, "Well, David, I see you didn't get the 'Tonight Show' again.'" When he said he told his mom that he had Bill Cosby as his guest, his mother replied: "'OK, maybe I'll switch from Conan.'"

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