Other mistake: In the opening, when they get into the car, it's obvious that there is no glass in the rear window.
Continuity mistake: Beaver gets his tonsils out in this episode, but in 3-29 "Beaver's Monkey", Beaver compared the situation in that episode to being just like when he had his tonsils out. Did they grow back?
Continuity mistake: When Margie Manners is shown mopping the Cleaver's kitchen floor she is using a sponge mop. When Wally comes in, the scene then shows Margie pushing a string mop against Wally's shoes.
Continuity mistake: When June is talking to Wally, she's wearing a wristwatch and her wedding ring on her left hand. But in a close-up shot of her hands while she's making a sandwich, her left hand is bare with no watch or ring. Back to the wide shot, and the watch and ring are on her hand again. (00:05:25)
Character mistake: The lady that talks with Miss Landers about the play calls Gilbert Bates "Gilbert Harrison."
Continuity mistake: When Beaver makes a face for The School Picture, he sticks his tongue out. But when Mrs. Rayburn and Miss Landers are looking at the picture sometime later, Beaver isn't sticking his tongue out. (00:13:00)
Continuity mistake: At the start Ward drives up in their old 1959 Plymouth Belvedere. He had been driving the 1961 Plymouth Fury for some time in season 4.
Deliberate mistake: Although it was done for plot purposes, no school photographer would only take just one shot of a class photo. They generally take up to 15 to 20, as it is difficult to get everyone to look at the camera and smile at once (and hopefully not pull silly faces).