Factual error: The show is set in the fifties but Fonzie has a Mustang hubcap on the wall of his garage. The first Mustang came out in 1964.
Continuity mistake: In Arnold's, throughout the series you can see the men's toilets on the left and the women's toilets on the right. But whenever Richie, Fonzie or any boy goes into the men's toilets, they make a right.
Factual error: When Arnold's is seen from the inside, metal pinball machines are seen. Since this show is set in the 50's, the pinball machines should be wooden. Metal pinball machines didn't show up until the 70's.
Suggested correction: Steel pinballs date back to the 1940s.
Factual error: The show takes place in Milwaukee, but several times palm trees are visible in the background. One blatant shot is over the wall at Arnold's.
Other mistake: The interior of the house (excluding the first season), has a door from the kitchen leading outside not far from the front door on the same side of the house and no windows facing that direction, but from the exterior of the house always shown, there is no 2nd door by the front door. Instead, a large window is shown where the kitchen door should be.
Other mistake: The outside of the house does not match the interior setting at all.
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)
Factual error: The Cunninghams are going to the movies, and Ralph asks Joanie what they are going to see. She says "Psycho" which was made in 1960. The series was set between 1955-1965, this episode would have been set in '57.
Other mistake: June Lockhart is referred to verbally as 'The Honourable Judge McKay', but the end credits say 'Judge MacBride'.
Other mistake: The background action in the opening credits is slightly unsynchronized. This is most obvious at the "Goodbye gray sky, hello blue" line in the theme song, as Potsie mouths the lyrics. It's also obvious at the "My cycle hums" line, as the girl in the blue plaid skirt shows up at "cycle", rather than "my." (01:13:10)
Visible crew/equipment: When Al, Fonzie, and Howard use "Gulper" in the diner's kitchen, it starts to throw salad all over. You can see the same hand twice in a short period throwing salad from the door window. (00:13:40)
Continuity mistake: In this episode, Fonzie has to go to the hospital to get his tonsils removed. In season 2 episode 6 "Haunted" Fonzie stated that he had his tonsils removed when he was a kid.
Marion: Fairy Godmother - S6-E21
Continuity mistake: Ralph is at Al's after everyone else has left on their dates. He's depressed and as he walks up to a table, you can see a couple of plates of food sitting on it. Then Fonzie comes in (hitting the wall to turn the lights on) and Ralph looks away from the table (he doesn't move otherwise). Then they show the table again - which is completely empty.
Visible crew/equipment: When Don comes into the garage to apply for the job, the T-mark can be seen on the floor by Fonzie's feet.
Revealing mistake: When Arnold's burns down you can see the set walls wobble a lot.
Ralph's Family Problem - S7-E25
Factual error: Fonzie takes Ralph on a motorcycle ride to make Ralph feel better, but they are roaming through hilly areas. There are no hills in or near Milwaukee.
Continuity mistake: There is a blizzard on Christmas Eve dumping two feet of snow on Milwaukee. Mrs. Cunningham, LaurieBeth and Al are stuck at the Cunningham's house. Near the beginning of the episode, they show an exterior shot before they go inside the house. The driveway for the house is wet looking but totally clear of snow, with no one there to clean it, and it's still snowing. The hardware store has two feet of snow outside of it.
To Beanie or Not to Beanie - S9-E12
Factual error: When Mr. And Mrs. Cunningham are talking to the Fonz in their bed about Joanie going to college, Mr. Cunningham is wearing a digital watch and those didn't exist in the 50s - 60s when the show takes place.
The Ballad of Joanie and Chachi - S11-E2
Visible crew/equipment: After Chachi walks out of the college classroom, when Joanie takes a seat and starts crying the boom mic dips into view at the top of the screen, in the wideshot.
The People vs. the Fonz - S11-E11
Factual error: When the Cunninghams are talking about Fonz's trial, Mr. Cunningham can be seen wearing a digital watch. Digital watches didn't exist in the 50's.
