They Have Been, They Are, They Will Be... - S1-E3
Continuity mistake: While Tony Vincenzo is eating, his butter knife instantly turns into a fork in the next shot.
Continuity mistake: When Richie gets up from a table at Arnold's to meet with the Fonz in the men's room he's wearing jeans. When he enters the men's room he's wearing grey slacks. (00:07:50)
Continuity mistake: A criminal steals Fish's gun and holds the squad hostage. He has a handcuff on one wrist with the other one hanging. The hanging cuff goes back and forth between being open and being closed throughout the scene.
Continuity mistake: Willona's ex-husband had 3 different names: Alvin, Ray, and Roger.
Continuity mistake: In "Twenty-One Today" (4-8) Williams says that he grew up in an orphanage and didn't know who his parents were, but in this episode he says that his father was a coal miner in South Wales.
Continuity mistake: In an episode of Mary Tyler Moore (from which Rhoda spun off) entitled "Rhoda's Sister Gets Married," Rhoda's sister Debbie, predictably, got married. In the show Rhoda, Rhoda had only one sister, Brenda, who was not married, nor had she ever been.