Giant Mailbox attached to my Sim's head.

That is a great question. I didn't have cheats enabled but I will try to duplicate it and see if I can make it happen again. I should add that after I went out of the game and back in, the mailbox was sitting on the ground and my sim was standing next to it. It was still huge. The original mailbox was still in its place and was normal size.  Getting the mail returned to normal.