Tom Dreesen was a groundbreaking comedian in the late 1960s, and wound up as the opening act for Frank Sinatra in later decades. It was an exciting life, but not always an easy one, as he explained on 'Late Show' (Weeknights, 11:35PM ET on CBS).

The biggest challenge for Dreesen, and in fact Sinatra's entire entourage, was the hours Ol' Blue Eyes kept. "Even when we were off the road, he never went to bed until dawn," Dreesen said. "Off the road or on the road, six o'clock in the morning he wanted you to hang with him."

After a particularly grueling cross-country trek, Dreesen finally had had enough for one night, and decided to go to bed. When Sinatra asked him why, he responded, "I got to get up early in the morning and go to the cemetery and visit those guys."

"What guys?" Sinatra asked.

"All those guys who died trying to stay up with you every night."