In an interview in the April 17-23, 1976 issue of TVGuide, Lorenzo Music said that a number of actors read for the part of Carlton, including Foster Brooks, who turned down the role. Music said he and the other producers decided to make Carlton a drunk because Carlton was going to be a voice only character and "that's the simplest kind of voice characterization there is".
Drinking doesn't cause hangovers; stopping drinking causes hangovers.
Rhoda's apartment (in early seasons) is numbered 9-E; however, in exterior zoom-in shots, the building depicted has only six stories.
As the closing credits creep up the screen, you see Valerie Harper, as Rhoda, stranded in the middle of a very busy intersection desperately trying to get to the other side.