A number of Walking Dead viewers were left wondering why some walkers froze completely and others were still capable of attacking Daryl (Norman Reedus), Michonne (Danai Gurira), King Ezekiel (Khary Payton) and the group on their icy trek towards Hilltop.
"The idea was that they would kind of freeze in place and be preserved over the winter, and when things thawed out, they'd just kind of come back to life and go about their business," Walking Dead creator Robert Kirkman explained aboard Walker Stalker Cruise 2018 when asked about winter walker physiology.
Kirkman, who has long featured snow-covered walkers in his ongoing comic book, compared the phenomenon to behavior exhibited by alligators during the "Bomb Cyclone," in which gators survived extreme temperatures by freezing themselves in place, entering into a mini-hibernation with their snouts protruding above the ice.
Both the books and the show have explored different "types" of walkers, including some who are less active; in the books, these less mobile walkers are typically referred to as "lurkers."
When Frank Darabont served as showrunner in the series' debut season, some walkers showed lingering signs of "intelligence": Morgan's (Lennie James) wife was seen pawing at the doorknob to her old home, while some walkers were seen using rocks in an attempt to breach the department store where Rick Grimes (Andrew Lincoln) holed up when trapped in Atlanta.
Though those attributes were quickly dropped and walkers have since become more homogeneous in their abilities, it could explain why some walkers outright froze in place and became totally rigid while others were able to emerge from snow and attack our heroes — even if it is a stretch.
A thawed out Walking Dead returns with its tenth season this October on AMC.