So I've been watching the first season of The Dick Van Dyke Show and it is fascinating. They filmed the first 14 episodes before the first episode aired. Just in those 14 episodes, though, they realized that Mary Tyler Moore was obviously a legit star so they moved the order around and moved up a spotlight episode from roughly episode #9 to episode #2. They also moved a couple of other episodes spotlighting Moore.
Which made me think - what was the quickest time that a supporting character was obviously a breakout star? Urkel? Fonzie? Would Kramer count (as he was a supporting cast member right off the bat)? John Cage on Ally McBeal (he was such a surprise character that they later had to address the fact that his introduction on the show was him hiring a prostitute, which dd not match the characterization of Cage once he was an established character)?
In Laura Petrie, the episodes hadn't even AIRED yet when they realized she was a breakout candidate, so I wonder if that means she "wins" this?
What do you folks think?