When the kids are putting on their Halloween costumes, Charlie
Brown's ghost sheet has many holes in it. Shortly after, when Snoopy is walking out the front door as the World War I Flying Ace, Charlie Brown holds the door open for him and salutes. When he does this the many holes in his ghost costume disappear, only to re-appear later.
In the opening scene in which Lucy and Linus go out to the pumpkin patch, we see the setting sun in the background, which the children pass as they walk. However, the sun (just like the moon when we drive a car) would not be "passed" as though it were a stationary object; rather it would "move" along with the person moving. A second setting sun appears at the end of the same shot, after the children turn a corner and walk in another direction.
When then scene during the Halloween party is shown, a girl with a green dress says, "Charlie Brown, you'll have to model for us". When she says that, she suddenly grows a third hand, then she has two hands again shortly after.