AS FAR AS YOU CAN TELL A HOUSE BECOMES HOTEL WHEN YOU MAKE IT WHAT YOU WANT TO: Since we're already degenerating into Lost-level minutiae about Diff'rent Strokes, here's something I was thinking about this afternoon.
I believe, but could be convinced otherwise, that Diff'rent Strokes was the first show to assemble the complete version of the paradigmatic family sit-com main set. Slightly raised main entrance at house right, door to the rest of the house at house left, stairway upstage (running from house right at the bottom to house left at the top), couch downstage. Off the top of my head, after Diff'rent Strokes this was the layout for Cosby, Charles in Charge, Married With Children, and Modern Family (I have a vague recollection that it was the setup for Eight Is Enough as well). I'm into deep memory here, but I think that this set design builds on the All in the Family prototype, which is the same except that the couch is a pair of recliners/chairs sharing a table.
Am I wrong?
