"Supernatural" - The Gay Subtext

I just started watching the show, and I know that at least in recent years they've toyed with the underlying gay subtext people have picked up on, not to mention all the gay fanfic out there. My question is, when did they start goofing on this? Was it right off the bat, or a few seasons later?

• In the first season, one of the first few episodes, someone mistook Dean and Sam as a gay couple.