Around the 'net, you can find many sites which say that when Carl Reiner and Sheldon Leonard were casting the program that eventually came to be called The Dick Van Dyke Show, it came down to deciding between Johnny Carson and Dick…and of course, Dick won out. I can absolutely believe that in their hunt for just the right guy to play Rob Petrie, either Reiner or Leonard or someone else said, "Hey, how about Johnny Carson?" They probably at some point had a whole list of names.
But I have trouble believing it ever came down to a choice between Dick or Johnny, Johnny or Dick. In various places, Mr. Van Dyke, Mr. Reiner and Mr. Leonard may have said it did but I don't believe it was that close a contest. Why? Because in December of 1960 when they were casting the pilot and in January of '61 when they filmed it, Johnny Carson was not available. He was hosting the game show Who Do You Trust? on ABC's daytime schedule…and you don't film a pilot with a star who is not under contract to appear in your series if a network orders a batch of episodes.
No network would ever even consider a pilot for The Joe Blow Show if the producers didn't have a contract that ensured they could deliver Joe Blow…and not just one season but for several should his show be a hit.
Now, I suppose it's theoretically possible that Carson's current contract to host the game show was coming to an end around that time and it's possible he was willing to take the gamble that the sitcom pilot would sell even though at no point in his career did he show the slightest interest in starring in a situation comedy…
…but I really doubt that. Most bios of Johnny say that after failing on any number of previous TV projects, he was delighted to have a hit with Who Do You Trust? He reportedly turned down several seemingly-better offers to leave it, including saying no to the first offers he got to host The Tonight Show.
And when he finally did decide to take the Tonight Show offer, the producer of the game show, Don Fedderson, refused to let Johnny out of his contract. That's why after Jack Paar left Tonight, they had six months of guest hosts until Carson's contract finally expired and he could take over. I just don't see any real possibility that he could have been a serious contender for the lead in Carl Reiner's situation comedy. Does anyone think that? No matter what anyone says?