Zombie pigmen can break down doors like the old zombies
What I expected to happen was...:
The pigman would wonder around like normal

What actually happened was...:
He approached a door and started to smash it with the well known very loud door breaking noise.

Steps to Reproduce:
1. Make a box
2. place a door as the only opening
3. Spawn zombie pigman and watch the magic or give him a nice punch in his rotting zombie face so he tries to kill you