Harpo Does Something Funny: Dwight Schultz has said one of the scariest things during the filming was how blank the scripts would often be.
Also, the writers frequently would not write the tag and then would just say to the actors "just make something up," or told Dwight Schultz and Dirk Benedict to loosely write up a tag.
Throw It In: An extremely frequent occurrence, if grudgingly. There was a heck of a lot of Improv going on by the actors and notably Dwight Schultz, and though the writers frequently got mad by how the actors would go off-script or ad-lib lines, they often (if grudgingly) agreed that it should be kept in.
Screwed by the Network: More like Actively Sabotaged by the Network. The show was considered politically incorrect (showing a positive view of Vietnam veterans, among other things) and its success completely unexpected; it was subjected to Invisible Advertising, the network officials and producers actually badmouthing the show to the press, it was made a 'bad move' to write for, so despite its popularity it eventually succumbed to cancellation.
Stillborn Franchise: While hardly a flop, the film only grossed $170 million on a $110 million budget. The cast and director expressed interest but ultimately concluded that it wasn't profitable enough to risk it.