I had all the same issues with this episode as well, nothing quite fit and although I didn't have a problem with the revelation from demon!nora about Lucifer being able to jump into Sam's body with him not actually being in it! I do find the whole explanation of that very sloppy and not very well thought out. I really hope if they do go down that route again, that they write it a hell of a lot better then they did here. Especially after the other revelation in ep13 about Sam and Dean's vessels. I'm so completely confused as to what the hell is going on now! It's episodes like these, which makes me realise that they really shouldn't bring in new writers to well established shows, especially if they can't do their research!

I think it would have worked a lot better with Jared acting as Gary the whole time as well. He'd shown he could do an excellent job of it, but then I also guess they would have had to of relied on the boy who played Gary to act as Sam and that's maybe where it might have fallen flat.

Oh and I love your point about no one ever having possessed Dean before. It does say a lot about his character.

For me, I'm just gonna take this episode for what it is. Just a bit of fun! I think if you take this episode too seriously, then you'll just go crazy!