I had to keep watching for Castiel's first appearance in 4X1. He's my favorite character
I definitely remembered this episode, so I guess I started to watch the series with Season Four then, but I think I still only watched the occasional episode at that point.
BTW has anyone seen this "Supernatural Anime" series? Apparently it's 22 half hour animated episodes that re-make the first two seasons of the show. Did this air in America? Is it any good? Too bad I literally just watched S1-2.