and now ladies and gentlemen, here's johnny! ♪ >> johnny carson wasn't just the host of "the tonight show." johnny carson was the man that america said good night to for 30 years. ♪ >> and on my watch, johnny decided that 30 years was a great time to take a bow and say thank you and good night. >> 30 years is enough. it's a good time to get out while you're still on top of your game plan. >> johnny carson retiring in the early '90s was the great moment where a huge chunk of the ice shelf breaks off. something that has been there for centuries, for thousands of years, suddenly is no longer there. >> a tremendous part of history. and that's lovely to have made your mark on an era like that.