“I was a better performer than I was a writer and Dave was a better wordsmith than he was performer,” says Leno. “When I first saw Dave at the Comedy Store, he had really funny material. When we met, he kind of said, ‘How can you get up and be so confident?’ I think … for me, standup was always a natural place to be. He didn’t really enjoy doing standup.”

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Elayne Boosler, also part of the Comedy Store scene, appreciated that when Letterman launched “Late Night” in 1982, he chose the best comics to appear — regardless of gender. That wasn’t the case on “The Tonight Show,” she says, which, with the exception of Joan Rivers, rarely featured female comedians.

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“I will forever be grateful to him in knowing that women are funny, and I think it was because he came up in the clubs with us,” she says. “Whereas people like Carson didn’t. When ‘Late Night’ started, there was no game in town and suddenly, he’s presenting woman after woman after Franklyn Ajaye, after Hispanic comic, after me. It was like, ‘America’s here, folks, not just blond, bland guys who don’t offend me.’ ”

Before he was a U.S. senator, Al Franken spent decades as a key writer on “Saturday Night Live.” He always admired Letterman and noted how much he appreciated his on-camera speech after the Sept. 11 attacks. But ask Franken about his favorite moment during Letterman’s tenure, he’ll immediately skip to the Monkey-Cam.

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“Because you’re cutting from the chimp on the tricycle to what the camera on the chimp’s head is showing,” says Franken. “It looks stupid and ridiculous and it’s endlessly entertaining. So it’s chaotic, but there’s a basic, brilliant idea behind this hilarious chaos. It’s basically this is color television.”

Chris Elliott began appearing on “Late Night” in the mid-’80s as “Marlon Brando” and “The Guy Under the Seats,” quirky characters who often mock-menaced Letterman. During his tenure, Elliott once found himself housesitting with his future wife, Paula, for Letterman and Merrill Markoe, the host’s partner and one of the “Late Show” creators. He wandered into Letterman’s office. “And I looked around and one thing I saw was that a dictionary was open and the dictionary had a work sheet next to it, and my assumption was Dave was learning words he didn’t know. And that he was testing himself. And you know, looking at the words and writing his definition and studying the dictionary.”

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Martin Short, known for his time on SCTV and SNL, found himself more excited to do Letterman than “The Tonight Show.”

“For a long time, I didn’t do Carson because I thought it was cool just to do Dave,” he says. “And then finally there was a rumor in late ’87 that Johnny might leave and then I thought, ‘Well, I’m an idiot. I’m just afraid of it. That’s why I’m not doing it.’ So I did both. But Dave was always the show for me to do and it was important to score. And no matter where you were in your career, you felt really, really, really proud of yourself and happy if you killed on Letterman.”

Robert “Morty” Morton, Letterman’s longtime executive producer, could see Letterman mature over the years.

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“It started with his way of opening up his conversations with favorite guests like Bill Murray, Steve Martin and Tom Hanks,” Morton says. “When you asked Tom Hanks a question of when he worked as a bell hop, he’ll tell the story about bending the shaft on golf clubs. The seismic shift was when Letterman realized I have a more powerful voice than just being a jokester. I have a very strong voice of a generation. When he came back in 9/11, he was bold enough and daring enough and didn’t need the reinforcement of laughter to get out a message. I think he took on a new responsibility.”

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When Letterman hosted his final “Late Show” in 2015, some thought he would step away from the spotlight. Jimmie Walker, one of his oldest comedy friends, admits he has been surprised by Letterman’s decision to do everything from a new show on Netflix to appearing at public events.

“I think all of us are a little shocked that he’s doing as much as he’s doing,” says Walker, who hired Letterman in the 1970s to serve on a writing staff that included Leno, Louie Anderson and Byron Allen. “I expected even less than what Johnny Carson did. That he would be totally insular. Nothing. I expected him to be what Cosby’s doing now. Just not heard from again.”

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But Steve Young, a longtime writer for Letterman, asked his former boss to show up as a guest for a class he teaches at NYU. Letterman did. Young still remembers the night Letterman announced he would retire from the “Late Show.”

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