Other mistake: In season 1, we learn that Beaver is in 2nd grade-Wally in 8th. So by the end of 6 seasons, Wally would be in college. Tony Dow and Jerry Mathers are actually 2 years+/-apart.
Leave It To Beaver (1957)
1 other mistake in show generally - chronological order
Starring: Barbara Billingsley, Hugh Beaumont, Jerry Mathers, Tony Dow
Other mistake: The opening credits for season 5 show June coming out of the front door with a pitcher of what looks like iced tea, and calling for Ward, Wally and Beaver who are all working outside. But the door opens by itself as she comes out, and then closes by itself behind her. If the entire family is outside, who opened and closed the door?
June Cleaver: Eddie, would you care to stay for dinner? We're having roast beef.
Eddie Haskell: No thank you, Mrs. Cleaver. I really must be getting home. We're having squab this evening.
Trivia: Phyllis Coates, who plays the new neighbor Mrs. Donaldson, played Lois Lane in the first season of the Superman TV series in the 1950s.