Anachronisms: When Ritchie becomes involved in politics, he has a 50-star (1960) American flag.
Anachronisms: The pinball machine in Arnold's Malt Shop is a Bally Manufacturing "Nip-It", which wasn't produced until 1967.
Anachronisms: Throughout the show's run, in most of the facade scenes, many of the cars seen passing by are clearly from the late '60s and early '70s.
Continuity: The architecture was incorrect. From exterior shots the driveway/garage of the Cunningham house was to the right of the front door, while from the interior sets the garage was still to the right of the front door (i.e. it would be on the left as viewed from outside).
Anachronisms: In one episode, the Cunninghams are on their way to the movies. When Ralph asks them what they are going to see Joanie tells him they are going to see Psycho (1960). However, the episode is set in 1957, three years before it the film premiered.
Anachronisms: In one episode set in 1962, the song "I Get Around" by The Beach Boys is heard playing on the jukebox. That song wasn't released until 1964.
Anachronisms: In his first appearance, Mork is looking at an episode of "The Andy Griffith Show" (1960). However, the episode takes place in 1959, and the Andy Griffith Show didn't premiere until a year later in 1960.
Continuity: The restrooms at Arnold's restaurant have the Men's room on the left, and the Lady's room on the right. But, in all of the shots of the guys coming into the restroom, they walk in making an immediate right.
Anachronisms: In the last year or so of the series, nearly all the characters sport modern hairstyles.
Continuity: In the pilot episode, the diner the characters attend is called Arthur's. In all subsequent episodes, the name has changed to Arnold's.