Now, if I had meant for it to be a "what if" then I would have worded it that way. But obviously I didn't.Okay, Mulder and Skully move from X-Files to Men in Black. They remain Mulder and Skully, played by David and Gillian, and remain the lead actors in MIB. One franchise to a completely different franchise, in different universe, with characters remaining the same and remaining the leads.Okay, so why don't you provide a couple of examples that you know of and illustrate the concept for the rest of us poor schlubs?
Dean and Sam Winchester move from Supernatural to Fringe. They remain the same characters, remain leads, but in completely different franchise in different universe.
Then the simple answer to your question is NO, it doesn't fucking ehappen and never has, for the simple reason that characters are valuable intellectual property, and lead characters are what you build the franchises on, and no studio, network or production company in its right mind would transplant the lead characters from one successful franchise to be leads in a completely different franchise because the most likely outcome of such a stupid move would be the death of both franchises, because you took the backbone of one and dropped into another where it completely wouldn't fit!
So no, Kirk and Spock never took over command of Alpha Moonbase, Jim West and Artemis Gordon never ran a herd of cattle on Rawhide, and the notion of Commander Adama in Hawaii ordering Magnum around is just retarded.
You asked a "What if" question in the form of a historical one. You shouldn't be surprised at the responses you're getting.
I think perhaps you and one or two others may have gotten too hung up on my examples which involve major franchises and major actors and characters. I used those as examples precisely because they are well known and would better illustrate what I'm talking about.
It may never have happened in the recent past between major American productions, but my question wasn't limited to major American productions only.
If a show (or shows) has been gone from the air for some time, with no chance of returning, there is no reason a deal could not be struck between production companies or networks IF the involved parties are willing.
OTOH, you didn't have to post this much simply because you didn't know the answer to the question.