What I expected to happen was...:
The iron golem spawns normally.
What actually happened was...:
I saw the iron golem for a second before the game crashed.
Steps to Reproduce:
1: go to creative
2: create an iron golem with iron blocks and a pumpkin head
3: game crash (may take a few seconds)
Can you supply a seed and coordinates for where this happened? I've tried on a 1.4.3 client here and it worked fine.