First time Hershel starts calling the undead Walkers.
First episode in which Daryl Dixon begins regularly wearing his iconic leather vest with wing patches on the back. Daryl briefly wore the vest in the second season premiere, when the group was traveling out of Atlanta, but he takes it off before joining the search for Sophia, and it is not seen again until this episode. He wears it regularly from here on.
When Glenn shoots at the door, the handle turns moments before showing an 'A' like many other places throughout the show
Daryl begins the episode wearing (largely) the same outfit he has worn from the beginning. Part way through, he switches to the vest/denim shirt/black jeans outfit, ostensibly because the weather is turning.