Can Smokey leave the island as he pleases?
I used to believe that the monster was contained to the island; it was his one and only home. In my rewatch, I am on S4. I just watched the scene in which Jack is off the island and the smoke detector goes off in his doctor's office. When going to change it, Christian is sitting in a chair and talks to a shocked Jack. If Smokey is indeed Christian and other deceased (as it would suggest -- the smoke detector seems to be a clue from the writers), then this would make it possible for him to travel to and from the island.
What do you guys think?