The Golden Girls: The original plan was for Rue McClanahan to be Rose and Betty White to be Blanche. Not only did the actresses feel better suited for the opposite characters, but Bea Arthur almost did not want to be involved for fear of the show only being "Maude and Vivian meet Sue Ann Nivens" (as White and McClanahan would resemble characters from their previous series).
Miami Vice was supposedly funded and the pilot produced after a brief meeting where it was described as "MTV Cops", with essentially no other details. This is true according to Brandon Tartikoff, who was the NBC executive that green-lighted the show.
The Star Trek: The Next Generation season 6 episode "Frame of Mind" is a combination of two Riker-centric episodes: "First Contact" (not to be confused with the film), where Riker goes on a undercover mission on an alien world which goes awry; and "Future Imperfect", where Riker finds himself inside a Dream Within a Dream. Coincidentally, both episodes were from season 4.