Ben is too easy of an answer to me as to who is in the casket. It makes a lot of sense, but this is Lost. Being that the events of the close of season 3 could have taken long after they were on the island, or even Kate's court case, I think that the casket belongs to Aaron. How they're screwing with timelines lately, it wouldn't shock me if that episode's flashforwards took place at different times. The casket seemed abnormally short to me and while Walt's name was tossed around here in the previous season's Lost thread, that doesn't make sense to me. Speaking of Walt, Harold Perrineau, the guy who plays his father Michael, has been a credited cast member since the first episode of this season after not being credited in season 3. He still hasn't appeared on screen but I have a feeling it's going to happen any time now.