(AP) -- David Letterman ended his 33-year career as a late-night television host Wednesday, ushered into retirement by four presidents who declared "our long national nightmare is over" and saying there was nothing he could ever do to repay his audience.

The show ran 17 minutes over the usual hour, much of it because Letterman took the time to thank the people who worked for him. As the tuxedoed Foo Fighters performed "Everlong"-- a song they first played on the "Late Show" when Letterman returned after heart surgery in 2000 -- a long montage of photographs from three decades of television history zipped past on the screen.

"The only thing I have left to do for the last time on a television program (is say) thank you and good night," he said.

Letterman presided over 6,028 broadcasts on CBS and NBC, the transplanted Hoosier making Top 10 lists and ironic humor staples of television comedy and an influence to a generation of performers. True to his self-deprecating style, he said Stephen Hawking estimated that tenure delivered "about eight minutes of laughter."

Letterman will be replaced in September by Stephen Colbert, who he endorsed by saying, "I think he'll do a wonderful job."

The taped intro of President Barack Obama and former Presidents George Bush, Bill Clinton and George W. Bush referenced President Gerald Ford's declaration to the country when he took office following the 1974 resignation of Richard Nixon. Letterman sidled up to Obama to say, "you're just kidding, right?"

Ten stars from Steve Martin to Tina Fey delivered the final Top 10 list of "things I've always wanted to say to Dave." Julia Louis-Dreyfus, with Jerry Seinfeld standing nearby, said, "Thanks for letting me take part in another hugely disappointing series finale."

No. 1 was Bill Murray: "Dave, I'll never have the money I owe you."

Letterman joked in his monologue that he's been on the air for so long that the hot show when he started was "Keeping Up with the Gabors."

"You want to know what I'm going to do now that I'm retired?" he said. "By God, I hope to become the new face of Scientology."

From his start on NBC's "Late Night" in February 1982, Letterman's comedy was about more than telling jokes. He attached a camera to a monkey's back, tossed watermelons off a roof and wore a suit of Alka-Seltzer to plunge into a tank of water. Celebrities used to being fawned over either clicked with his prickly personality or didn't, and when Cher called him a more profane version of "jerk," it became a memorable moment.

He shifted to CBS in 1993 when NBC gave the "Tonight" show to Jay Leno instead of Letterman, a slight he never forgot or forgave.

Letterman even began his final monologue Wednesday by joking, "It's beginning to look like I'm not going to get the 'Tonight' show."

The tricks subsided as Letterman mellowed with age and fatherhood. His audience welcomed him back after a heart bypass, listened as he became the first late-night host back on the air after the 2001 terrorist attacks and saw him acknowledge to inappropriately having sex with a subordinate.

"When I screw up now, and Lord knows I'll be screwing up, I'll have to go on somebody else's show to apologize," Letterman said.

With his monologue and Top 10 list, the final show kept the same format of thousands before them, although he gave no one the pressure of being a guest on the final show. Murray played that part Tuesday night. His last few weeks have been warmly nostalgic, with Letterman entertaining old friends like Tom Hanks, George Clooney, Julia Roberts and Oprah Winfrey. Anticipating the end, viewers sent Letterman to the top of the late-night ratings the week before last for the first time since Jimmy Fallon took over at "Tonight" and they competed with original telecasts.

Letterman, before saying goodbye, thanked virtually everyone involved with the show from CBS Corp. Chairman Leslie Moonves to his researchers and crew members.

"It's so obvious every night and again tonight that they were so much better at their jobs than I am at my job," he said.

Letterman remained dry-eyed throughout the broadcast, but several audience members who filed out of the Ed Sullivan Theater had tears in their eyes.

"He was guarded but you could tell it was really hard for him," said John Bernstein, who flew in from Los Angeles to attend the final taping. "You could see his emotion. But I think he's feeling a lot more than he's showing."

Rival Jimmy Kimmel paid tribute to Letterman by not making a fresh ABC show on Wednesday, when he usually competes in the same time slot. Fallon opened his Wednesday monologue by saying: "I want to thank you for watching this on your DVR after you watched Letterman."

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