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.
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.
Continuity mistake: As Beaver and Wally are starting upstairs after Ward asks them to go change their shirts for supper, the camera cuts from a long shot of Ward across the room in a chair reading a newspaper, wearing a light grey suit, to a medium close-up of Ward wearing a much darker suit, and then back to the light grey.
Captain Jack - S1-E3
Continuity mistake: When Wally and Beaver are caring for the baby alligator in the bathroom, Beaver holds out his left index finger and it gets nipped by Captain Jack, but next shot Beaver's holding his injured right index finger. (00:11:30)
Captain Jack - S1-E3
Continuity mistake: Ward jokes about the boys having two baths in three days, being some kind of record. It then cuts to the boys sitting on the floor in the bathroom, and we can see the hamper at the right with nothing atop it, but when Wally stands up to put CJ back in the "aquarium" the tank lid is lying on the hamper. (00:11:35)
Captain Jack - S1-E3
Continuity mistake: Where's the puppy that the boys get at the end of this episode throughout the rest of the series?
Suggested correction: In episode 1x23, Beaver and Poncho, when Beaver brings home a lost little Chihuahua, he shows his parents and asks to keep him. Then Ward tells him, "You and Wally had a dog once, remember? You didn't take care of him. We had to give him away." This explains what happened to the dog from season 1, Captain Jack episode.
Continuity mistake: During the dinner scene, in the wide shots of the family there's a mirror hanging on the wall above the sideboard behind June, but in the shots facing June the mirror is gone. (00:02:15)
Continuity mistake: Beaver has a frog in hand when Wally is on the phone, then it is not there when Wally hangs up the phone. (00:10:35)
Continuity mistake: When Beaver goes to Penny's front door, the door changes in appearance from one shot to the next. (00:23:05)
Continuity mistake: When Beaver walks over to the window to look outside, the window is fogged up due to a rainstorm. But when he gets there, the pane of glass he looks through is clear - without his having had time to wipe it off. (00:03:05)
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)
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 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: When Aunt Martha enters the front hall, as June is leaving, the shadow of a mic boom is visible as she comes in and as she leaves. It's visible on the top left.
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 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: 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: 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)
Continuity mistake: As the boys are playing basketball at the Cleavers' house, Tooey is shown in the first shot without his glasses, but immediately in the next shot where he shoots for a basket, he is wearing them. Magical glasses, indeed.
Visible crew/equipment: When Mrs. Bennett shows up the second time and tells June that she'd like to give Beaver a reward, the curved chalk actor's mark is visible on the floor near the staircase, and it's where June will stand after Poncho and his "mother" leave the house. (00:21:05)
