We saw alot of old Doc Shephard last night, but I think we saw two different things.

When Claire sees her father, Christian is dressed differently, and his hair seems to be all white. I think this is whatever is living/staying with Jacob in the cabin.

And what Jack is seeing is the Island personified, or the Smoke Monster as many believe it can assume different shapes. Also Claire's Christian is holding Aaron. Has the monster or the island ever interacted with anything, other than Kate's Horse (but I always thought that was more of a magic box thing and not the Smoke Monster..) ?