Robin Williams in character as disc-jockey Adrian Cronauer in director Barry Levinson’s comedy drama, “Good Morning Vietnam.” (Touchstone Pictures/AP)

“Late Show With David Letterman” was in reruns last week, so the late-night host took time out of his show Monday to reflect on the sudden, tragic death of Robin Williams.

Letterman talked about his friend of 38 years, who appeared on his shows approximately 50 times. He explained that two things would happen when Williams was a guest on the show:

“One, I wouldn’t have to do anything. All I had to do is sit here and watch the machine. And two, people would watch if they knew Robin was on the show, the viewership would go up because they wanted to see Robin,” Letterman said.. “And believe me that wasn’t just true of television. I believe that was true of the kind of guy he was. People were drawn to him because of this electricity, whatever it was that he radiated that propelled him and powered him.”

Letterman also shared some great stories of their early stand-up days, in addition to when Williams invited him to appear on “Mork & Mindy,” and aired a montage of previous Williams moments on the late-night show.

Watch the whole thing here: