In preparation for Season 4, David Morrissey lost weight to show the hardship the Governor faced. While the weight loss was real, the hair and beard were fake, specially made for him in London.
The Governor (David Morrissey) uses the name Brian as an alias. This is a reference to the novel "The rise of the Governor" in which Brian is his real name and Phillip is the name of his dead brother.
The fire that destroyed Woodbury was mostly visual effects, since it was shot in the real town of Senoia, GA. But the town hall was a set that was actually burned to the ground.
The skull-crushing moment needed more than just a prosthetic walker head for full impact. A fake hand was also used to prevent injury as it hit the solid wall of the pit.
The chess set used in this episode is a replica of the "Lewis chessmen", a 12th century chess set found in Scotland.