In the 1975 episode: "Mike's Pains" - Archie (Carroll O'Connor) goes "off script" and ad-libs a line that forces Mike (Rob Reiner) to break character. The original script:
Archie: "... because I can't stand people who are always knocking minororities" (sic)
Mike: "Gloria! You better get down here. I can't stand being with this guy alone."
But Carroll O'Connor ad-libbed: "What's the matter ... my fly open?"
