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."

Question: Do you think any one of the five remaining American Idol contestants have any idea who were in the original Rat Pack?

Answer: Sure, Emilio Estevez, Judd Nelson, Anthony Michael Hall, Molly Ringwald, Ally Sheedy, Demi Moore and Rob Lowe.

No, that was the Brat Pack. American Idol is honoring the original Rat Pack, which is actually not the Las Vegas Rat Pack. The Frank Sinatra, Dean Martin, Sammy Davis, Jr., Peter Lawford and Joey Bishop pack of the 1960's Sands Hotel was in fact an outgrowth of the Rat Pack that Humphrey Bogart and Sinatra first formed in the late 1940s.