Pretty sure that this is everyone's favorite iteration of Dean Winchester. Demon Dean only lasted about two episodes but even in that amount of time there was a change in his style of dress that lasted throughout his darker Season 9 arc. Like Will Graham, Dean Winchester is mostly seen in jeans, flannel and hiking boots, reflecting his Midwestern roots. During the darker season however, his shirks all of the above for slimmer, black jeans, leather and darker toned t-shirts. Since he is very firmly not a demon for most of Season 9, this change in costume style seems more so to reflect his darker mood as he deal with the curse on the Mark of Cain. We have to say though, leather jackets definitely look good on this character.
Castiel: It's very complex. If the pizza man truly loves this babysitter, why does he keep slapping her rear? Perhaps she has done something wrong. Dean: Are you watching porn? Why? Castiel: It was there. Dean: You don't watch porn in a room full of dudes. And you don't talk about it. Just turn it off. Well now he's got a boner.