I recommend The Onion A.V. Club’s “Random Roles” interview with John Larroquette, who has been doing TV for approximately 900 years and whose reminiscences cover a lot of ground, from the retooling of his self-titled sitcom — whose first season was, as he says, one of the best and darkest network shows ever, and which essentially had to sell out its creativity in order to continue — to the tricks a bit-part actor plays when he wants to make sure the audience at home gets a good look at his face. He also talks about his most famous (and multi-Emmy-award-winning) part, on Night Court, and how the character developed in a way that had nothing to do with the way the creator originally conceived:
And also, the character went through quite a metamorphosis. If you look at the early episodes, my character was this sort of tight-lipped, vested, pipe-smoking, conservative fellow. And of course I was putting garden hoses down my pants by the end of the series. I think what happens on a television series like that is that the creator of the show gets used to the characters and the actors playing them. They learn to write toward their strengths, which a good writer does. And [show creator] Reinhold [Weege] saw that I was this maverick, crazy—that sounds self-inflating, but I have a rather acerbic sense of humor. Reinhold starting writing toward that and creating the character that everybody knows.
There’s nothing very surprising about that; characters on TV develop to fit the actors and their strengths, whereas in movies, only the stars get parts tailored specifically to them (and maybe a few particularly distinctive character actors); the others have to find ways to reconcile their own personalities as actors with the way the part is written. Whereas on TV the writers, if they’re any good, have to do more adjusting than the actors: the actors are the ones who will be there every week, and they may be there after the writing staff has completely changed, so the writers need to make sure that the parts allow the actors to do what they do best. If it’s a choice between the creator’s original conception of the character and the strengths of the actor playing that character every week, a smart showrunner will choose the latter.
It reminded me of something that Paul Lieberstein said last year about The Office, that a huge factor in the development of the character of Michael was the writers’ increasing understanding of what Steve Carell did best:
An audience member asked how they broke away from the awkwardness of the original UK version and Paul credited it to the summer release of The 40 Year Old Virgin. They suddenly saw the warm and funny side of Steve and they used that as a model for how to write for him. They allow Michael to climb out of the holes he digs for himself, while David Brent just got lower and lower until he was fired. But they wanted to keep Michael around, so he couldn’t be quite so awful anymore.