In episodes in which the voice of Norm's unseen wife could be heard, her voice was portrayed by George Wendt's real-life wife Bernadette Birkett.
Cliff wasn't in the original script. John Ratzenberger auditioned for the part of Norm and wasn't thought suitable. He then asked the writers if they had a "bar know-it-all" and quickly improvised a character. This impressed the producers to the point that they created the part of Cliff Clavin for him.
From the start of the series, writers and producers made it a point to never show anyone leaving the bar drunk to drive home. The series would come to be recognized and cited by anti-drinking and driving groups for depicting and helping promote designated driver programs.
Kelsey Grammer's alcoholism became a problem during the final season. Co-stars noticed that he was oddly difficult to work with and would often be nearly catatonic between takes. After several intervention attempts, Grammer finally got help. He would ultimately not make a full recovery until the early seasons of Frasier (1993).
After Ted Danson announced that he was leaving the series, NBC wanted to continue the series by having Woody take over the bar. But Woody Harrelson refused to continue with the series without Danson.