On "This Place is Death" when Christian Shephard enters the cave after Locke has fallen through the well, the back of his head looks different between the first shot and the next one when he turns around. It looks like the hair on the back of the head is patchy in the first shot, either a really bad haircut or someone who's hair is falling out in clumps.
I'd really appreciate someone posting a screen grab of this shot or posting a link to one so I could hear some feedback on this, or at least pausing the shot on your television and posting an opinion, for those of you with that capability.
Patchy hair is supposed to be a symptom of Adams-Oliver Syndrome, along with too many or too few fingers and/or toes. This may be a hint as to the origins of the 4-toed statue as well as who may be behind the appearance of walking talking dead people both on and off the island.