On Jan. 14, 2000, David Letterman visited his doctor for what he assumed was a regular checkup.

He had a slight heart condition for a few years and it required monitoring, and that’s what he expected would happen that day. Instead, he found himself rushed to surgery in New York City, where he underwent an emergency quintuple bypass procedure.

The operation was successful; five weeks later, Letterman returned to host The Late Show on CBS. During his absence, the show was filled at first with reruns and then with new programs guest hosted by Regis Philbin, Robin Williams and Jerry Seinfeld. After Letterman came back on Feb. 21, he booked even more guest hosts so he wouldn't have a full schedule during his recuperation.

“Wait till you hear what happened to me!” he said at the start of his returning monologue. “You are not going to believe it. I’ve been away for a while. While I was gone, I had quintuple bypass surgery on my heart. Plus, I got a haircut. Ladies and gentleman, after what I have been through, I am just happy to be wearing clothing that opens on the front.”

He continued: “I won’t lie to you: When you find out you’re going to have the quintuple – the quintuple – bypass surgery … You know, guys come up to me and they say, ‘You know, Dave, I had the same surgery,’ and I say, ‘Oh, really? How many bypasses?’ ‘Two.’ I laugh at ‘em! ‘Two? You’re not trying! Pick it up a little!’”

Letterman noted that his career flashed before his eyes and that it had been “mostly awkward silences.” He joked that he discovered a “whole new respect for President Clinton. I spent half an hour with Hillary – look what happened to me!”

His first guest that night was Seinfeld, who pretended to believe he was there to host the show. “What are you doing here?” Seinfeld asked Letterman. “I thought you were dead.” “I’m on CBS, I ain’t dead,” the host replied. As he walked off, Seinfeld said to bandleader and sidekick Paul Shaffer, “You know where to reach me, right?”

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After showing that staff in the building opposite the studio had put up a sign across their windows reading “Keep it pumping, Dave,” he introduced eight of the medical team that worked on him, saying he knew he was getting on one nurse’s nerves when she told him, “You know, you can have as much morphine as you want!” His light spirit broke slightly as he told the audience that "it was five weeks ago today that these men and women saved my life. ... You tell yourself, ‘I’ll never going to be able to get through this.’ But you do get through it, and the reason you get through it is because these people get you through it.”

Watch David Letterman’s Returning Monologue

Philbin was the next guest, as Letterman rued the fact he wasn’t allowed full-strength coffee anymore. “First time I’ve done the show without regular coffee,” he said. “Decaffeinated -- I don’t care, sue me -- it stinks.” Then Williams appeared dressed as a surgeon, carrying a box of human organs that he said contained Michael Jackson’s nose, David Crosby’s sperm and one of Cher’s ribs. He joked that Letterman should be grateful he didn't see him in the operating room, and proceeded to mimic leaning over a hospital bed, pulling down his mask and saying, “‘Hey, Dave, it’s me! Think it’s gonna be real funny!”

The musical guest, by Letterman’s request, was the Foo Fighters, who canceled South American tour dates to make the show. Dave Grohl’s band played “Everlong,” one of the host’s favorite songs, before the credits rolled. Every member of the audience went home with a commemorative shirt with a surgery scar on the chest and the date of the procedure on the arm.

Asked by Oprah Winfrey in 2013 if the surgery was “humbling,” Letterman replied, “My heart surgery I loved. I loved everything about it. It was fantastic; it was dramatic. I was the star of it! I got to talk about myself every day to everybody!” More seriously, he noted that he "met some wonderful people who are still good friends of the family.”

“I was a hypochondriac,” he added. “You go through heart surgery, that takes the edge off your hypochondria – now you really got something. What I learned was, these people who do this [surgery] are so good, so talented, you have no choice but to trust them. They literally have your heart in their hands. I was so scared, then I realized when it was all done that I had nothing to be afraid of at all. These people are unbelievable.”

Letterman ultimately reflected that "everything good has come subsequent to my heart surgery … this is a landmark for me, personally.”