This might be the oldest episode of Johnny Carson's Tonight Show I've ever seen. It's from January 14, 1964 and while the video isn't great, it's amazing that this exists at all. You'll notice the show has a very different pace from Johnny's later broadcasts and from any other talk show of the last few decades.
Johnny makes reference to his announcer Ed McMahon and bandleader Skitch Henderson sitting in for him the past few nights. I vaguely remember nights like that and I also recall a few times when Ed guest-hosted all by himself. For some reason, Ed in later years (and in his autobiography, I believe) complained that he'd never been asked to guest-host. I don't know what that was all about…