You believe that? Ever watched the credits at the end of these shows? Notice the names of "writers". What do you think these writers do, write the credits titles?
The writers helped to write the monologue and the skits. The guests were entirely on their own. I remember some nights where Johnny had a hard time with some of the guests. Anyway, Johnny would ask guests before the show what they might want to talk about (like George’s AFPA jacket) and he used that to keep the conversation going. It was shown on one of his specials how he put his show together every night. Quite different from today where guests just come on to plug something.