In the episode where Mr. Burns makes everyone go on a walk in pairs up Mount Useful, to improve teamwork. After 1 or 2 avalanches, Homer opens the door, it opens how the hinge MUST be on the right. But, just a few seconds later, he opens it again, and it opens as if the hinge has swapped sides, and moved to the left. I noticed first time I saw this episode, it's so obvious.