Your post above (reply #7) is a great post too, MaggieEvans!
It's so true that Willie is one of the most believable characters on "Dark Shadows," and we see so much growth from him from when he first appears on the show, through the time he is in thrall to Barnabas, on towards the middle/late part of the series when he's spending a good bit of time away from Collinsport, and has found a girlfriend (whom we never see).
The first guy to play Willie Loomis (James Hall?) wasn't up to much, IMO. But John Karlen just gave him so much life and, well, realness, for want of a better word. He starts out being a sleaze, and ends by being one of the most sympathetic characters on the show. You really want things to come out right for him, and get the feeling he's had a hard life. He doesn't know quite how to overcome his past, but we can see that he is actually an innately good person.
Does anyone know, has JK ever talked about any backstory he may have worked out for the character?