Steve Allen was the brilliant original. Ernie Kovacs was way out there:
http://www.youtube.com/watch?v=z7xLDwzB5Cc
Steve Allen was better than Johnny. There, I said it.
People forget that for many years the Tonight show went on for 2 hours and usually after the monologue and the first guest, it degenerated into a dull, dull snooze-fest. I imagine that 95% of the TV audience was asleep by the time the third guest arrived. The final guest was typically someone you never heard of promoting a book that could put you to sleep if Johnny couldn’t.