Spoilers ahead
Pretty obvious appearance of “The Observer” last night. Watched for him during the whole show, and there he was at the very end.
All the way through the show, I kept thinking, “That kid is an Observer.” Chances are that he “beamed in”, or however that alien race comes in from their world. He might have been down there the whole time, simply unable to grow up for the very reasons Walter stated, or he could have just beamed over recently.