"This isn't actually about who's in the coffin, but something else that happens during that episode that no-one seems to remember. Jack is about to kill himself by jumping off a bridge. At that moment, a woman and her 8-year old son are driving towards him and they crash into his motionless car. He saves them. I have a theory that the woman was Juliet's sister and that the 8-year old son was her son. I actually don't know why I'm saying this, but I don't think we're going to see the last of them. That's all.

Oh, and to say I'm contributing to this mystery, let's forget everything I just said and say that the person in the coffin was Juliet's sister. :P I actually don't think that. I think it was Michael."