Goofs

The changing of the interior of the house after the second season messed up the scheme of the house. 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).

The restrooms at Arnold's restaurant have the Men's room on the left, and the Ladies' room on the right. But, in all of the shots of the guys coming into the restroom, they walk in making an immediate right.

In the pilot episode, the diner the characters attend is called Arthur's. In all subsequent episodes, the name has changed to Arnold's.

The exterior shots of the house don't match the inside layout. On the exterior, there are windows on both sides of the door. The interior layouts don't have any windows on that side of the house anywhere near the door.

After season 2, the interior layout changes. Seasons 1-2 have the stairs to the left as you come in the door, with a fireplace next to the stairs. Later seasons have the stairs to the right as you come in the door, and no fireplace. Also, thee closet the burglar gets trapped in by Fonzie was replaced by a window on the side of the house. Last, seasons 1-2 have no pass through from the kitchen to the living room. Later seasons have added it.

In the early seasons of the series, it's clear that many of the actors/actresses portraying teenagers are actually in their 20s+. This is done as to not interfere with the schooling of real teenagers and to give the general viewing audience who are teenagers (or young people) themselves someone they can look up to.

All though Postie, Ralph and the Cunningham Family are close to Fonzie, with him being friends with Potsie, Ralph and Richie, a real Middle Class family, in the 1950s, would not have associated themselves with hoodlums.

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.

From season 5 on there are plenty of color television sets seen in the series. Color Televisions didn't become in style until the late 1960's after the setting of the series takes place.

Chachi has a modern 70's-80's hairstyle and wristbands that street kids of the 50's and 60's didn't wear.

From season 5 on many of the male characters not only have modern feathered or Afro hairstyles, they're also wearing more feminine clothing which men didn't wear in the early 1960's.

In the last year or so of the series, nearly all the characters sport modern hairstyles.

The stairs to Fonzie's apartment appear to be located on the left hand side of the garage.But people appear to enter the top of the stairs from the opposite direction.

Despite being set in Milwaukee, Wisconsin, which is in the Midwest, many characters have New York accents.