So I was in a NPC village and then some zombies were attacking some villagers by breaking down a door so being me and being nice I killed the zombies and the breaking animation that comes up was on the door so I broke the door to find:
Known bug since 12w06a. They no longer break down Iron Doors as of 12w07a. However, no word of fixing this graphical error.
This first appeared in a 1.2 pre-release I think they fixed it and it came back in one of the 1.3 snapshots.