Where does the mailbox come from?
When Linus and Lucy are leaving their house for the pumpkin patch, their way is very clear. However, when they come back, it's apparently through the Twilight Zone. Now, there's a fence existing where there was no fence, and a sidewalk leading up to their door that wasn't there before.
But the weirdest thing happens later, when Linus mails his letter to the Great Pumpkin. Lucy follows him outside, and they go but a few feet away from the house, and there's a mailbox. That mailbox didn't exist before, when they went out for their pumpkin!