For me it's been a slow realization with clues all around. As a college student, I once masturbated to female porn with fishnet stockings and a slip. Not that I was particularly interested in cross dressing -- but it was a nice treat and I enjoyed the feeling of the soft silky material as it draped over my cock. At that time I also first tried anal insertion and it really blew me away! I didn't have too many opportunities for the "slip treats" but did make the time to try various items to play with up my ass -- but always with female porn. Lesbian was my preferred type with strap on being the main attraction. I was looking for strap on porn when I stumbled across shemales. I was aware of it but it was never really on my radar. Some was mixed in a new site I was on and what looked like some very hot girls turned out to really be my own shemale surprise. I was intrigued and my raging hard on was the proof.
It took a a few sessions to build up the courage to allow myself to cum with this new material, but once I did I knew I was hooked. For the record, Christina Bianchini was the first one to catch my eye and Mara Dorantes was the first one to come with.