I think the biggest problem with the Tommy Westphall multiverse hypothesis is based on what you would consider a crossover, or even a Continuity Nod
. Obviously, a Shout-Out
isn't always a continuity nod.
Example: A few shows are connected to the theory simply because they all use a Shout Out to a book for a company name... Those shouldn't belong at all. Drawing from the same source for inspiration does not translate to shared continuity.
But something like, how the St. Elsewhere cast hung out in Cheers, and Cheers' connection to Frasier, or the Elsewhere connection to Homicide (and not to mention John Munch.)
That being said, what I personally consider crossovers and continuity nods still makes up for a fairly large chunk of television.
Actually, the entry on the trope page for All Just a Dream
links to a site that (allegedly, I can't really tell) takes this into account and gives a rather conservative estimate.
edited 1st Dec '12 7:23:41 AM by sorin255