When Wally leaves the tennis court dejected after seeing Carol kissing the tennis pro, he is carrying two tennis balls in his left hand. As he leaves, his left arm brushes against a bush and he drops one of the two balls on the ground. When he shows up at home, he is back carrying the TWO tennis balls again.
When Wally arrives at the tennis court for his date with Carole, the bench he stands on is positioned between two fence posts. In the next scene it's right in front of a fence post.
Eddie and Lumpy come over to talk to Wally and ring the doorbell. Then they see Beaver walk up, so they talk to him instead. But nobody answers the door, even though both Ward and June were home, as shown when Wally comes home shortly after that.
When Beaver answers the telephone, the handset cord is pulling out of the handset. After Wally picks up the handset - the cord has been repaired.