David Letterman dedicated 10 minutes of his show to giving a moving tribute to late comedian and actor Robin Williams, who the Late Show host had known for 38 years.

David Letterman's Robin Williams Tribute

Letterman, 67, revealed on the Late Show Monday night that he first met Williams when the two of them were up and coming comics trying to make it in Los Angeles performing at The Comedy Store. When Williams was first introduced, Letterman was so blown away by Williams that he was too intimidated to talk to him.

“All of a sudden he comes up on stage and you know what it is. It's like nothing we had ever seen before—nothing we had ever imagined before,” Letterman said. “We go home at night and are writing our little jokes about stuff, and this guy comes in and we're like morning dew—this guy's like a hurricane. And now, the longer he's on stage, the worse we feel about ourselves. Because it's not stopping!"

Not long after making his debut at The Comedy Store, Williams landed a part on Happy Days and later a starring role on the spinoff Mork & Mindy. Though he achieved an incredible amount of success, Williams never boasted of his unique talents. "He was always so gracious, and we would talk about the old times, and never did he act like, 'Oh, I knew you guys were scared because I was so good,’” said the Late Show host. “It was just pleasure to know the guy. He was a gentleman and delightful."

Over the course of his stellar career, Williams made 50 appearances on Letterman’s show. Letterman admitted that when Williams was on, he could more or less take the night off, letting him carry the interview. Furthermore, shows with Williams on the bill always seemed to cause a spike in the ratings.

"People were drawn to him because of this electricity, this whatever it was that he radiated that propelled him and powered him," said Letterman. "Beyond being a very talented man and a good friend and a gentleman, I am sorry I—like everybody else—had no idea that the man was in pain and that the man was suffering. What a guy."