Morgan (Lennie James) painted the letter 'A' on one of the trees in walker blood. The occurrence of the single letter 'A' throughout the show has been common, but its significance has not been revealed.
As revealed by Lennie James on Talking Dead (2011), this episode was shot out of order - episodes 5, 6, 7 and even 8, the mid-season finale, were shot before this. The first person to see Scott M. Gimple's script was Greg Nicotero, after which the actors were not allowed to see it until filming, creating speculation among the cast about what episode 4 would be like.
The character Eastman's name is an anagram for Namaste.
This is an extended 62 minute episode (uninterrupted running time). The second extended episode of season six and the fifth overall.
The real name of "Tabitha" the goat is Ruby.