Continuity mistake: In season 1 (1957), Beaver is in grade 2 and Wally is 13 and in grade 8. Tony Dow was born in April 1945 and Jerry Mathers in June 1948. This means that Beaver/Jerry would have been 9 and Wally/Tony Dow 12, with a 3-year age gap. In the last (6th) season, Wally is a senior which indicates that he must have failed a grade. Meanwhile, Beaver is in 8th grade. Interestingly, the actors were also 3 years apart in age. At age 12 in 1957, Wally should have been in 6th/7th grade, which is more consistent with him being a senior in season 6.
School Play - S2-E11
Visible crew/equipment: At the start, while Whitey is reading aloud about the school festival, there's a large chalk T-mark on the floor in front of the boy at the center, and a small T-mark on the floor between Whitey and Beaver. (00:00:45)
Visible crew/equipment: After Ward has a word with the boys about having consideration for another person's happiness, when Wally and Beaver enter the kitchen, we can see chalk marks and T-marks on the floor near the counters. (00:22:10)
Visible crew/equipment: When Ward joins June in the kitchen he asks what's up with Wally, and his actor's mark is visible on the floor, then as June walks away, her T-mark becomes visible on the floor as well. (00:06:00)
Visible crew/equipment: In the kitchen, when June tells Ward the boys finished breakfast and went back upstairs with Tom Sawyer, there's a chalk T-mark on the floor near the sink. (00:07:45)
Visible crew/equipment: While Wally and Beaver are in their bedroom, when Ward comes in to talk to them the actor's tape mark is visible on the rug beside desk, where Wally is writing the letter. (00:01:45)
Visible crew/equipment: After June tells Ward the TV set is broken so the boys have nothing to do, when Ward enters their bedroom we can see a crew member's hand in the hallway reach up to close the bedroom door. (00:01:40)
The Grass is Always Greener - S2-E15
Visible crew/equipment: When June and Wally enter the kitchen while Ward is fixing the faucet's washer, the white T-mark and another actor's mark are visible on the floor near the sink. We see it again when Ward gives Beaver the small trash bin to take out. (00:05:10 - 00:07:20)
Visible crew/equipment: After Beaver's bath, when the family has lunch in the kitchen the chalk T-mark is visible on the floor near Beaver, which will be where Ward soon stands. (00:07:30)
Visible crew/equipment: Opening Scene: when Ward leaves the kitchen and comes pack in through the swinging door, you can see the shadow of the camera in the door just as Ward is coming back in.
Visible crew/equipment: When Beaver's class takes the intelligence test, a chalk T-mark is visible on the floor between the wall and Judy's desk. (00:09:40)
Visible crew/equipment: Early in the morning, after Ward and Wally go downstairs to check the trap June walks out of the bedroom (a funny June moment), and when Beaver rushes out carrying the baseball bat, the moving boom mic casts a shadow in the top left corner of the screen. (00:04:20)
Visible crew/equipment: While Wally and Beaver are at Sunday school, June and Ward go to the boys' bedroom to see how messy it is, and two chalk T-marks are visible on the floor where both Ward and June will stand. (00:21:10)
Visible crew/equipment: When Ward tells June he wants to take the boys to Friends Lake, for an overnight camping and fishing trip, as Ward heads for the staircase so he could tell the boys, he passes a c-stand, a piece of filming equipment visible at the right side of the screen. (00:08:25)
Continuity mistake: After Ward puts a new lightbulb in the fridge June stares at the mess Ward made, and the scalloped range hood vent is conspicuously missing, but when Beaver walks into the kitchen, the hood vent is back in its proper place. (00:17:10)
Visible crew/equipment: When a few of the kids pass the note from Linda to Beaver he puts it in his pocket, then it cuts to the class bell ringing, and there are multiple chalk marks on the floor where Beaver and other kids stand. (00:03:00)
Visible crew/equipment: When Ward enters the house June tells him she just got off the phone with Agnes Haskell, and the moving boom mic casts a shadow at the top of the screen. (00:21:45)
Visible crew/equipment: After Beaver is tossed out of the Blue Moon it cuts to Beaver walking up to Charlie, and the curved chalk actor's mark is visible under the desk, at Beaver's feet. (00:15:45)
Visible crew/equipment: Beaver asks June about some wealthy people in town, and when Ward walks into the kitchen, the moving boom mic casts a shadow at the top, left corner of the screen. (00:11:00)
Visible crew/equipment: After Eddie tells Wally that it once took his father two days to make a breadboard, when it cuts to Beaver walking into the kitchen, the curved chalk actor's mark is visible on the floor where Beaver stops. (00:09:35)
