Possibly the most unoriginal story, but the first Kaa encounter was my first boner ever. I used to watch several VHS tapes obsessively, and Jungle Book was one of them. I didn't know what my hard dick meant, I didn't even *see* it was hard, I just knew I liked that part of the movie more than any other (the second encounter wasn't on the same level). It just made me feel all cosy and warm.
Soon after I discovered masturbation and that scene was one of the first things I played in my head while doing it. I realized then that hypnosis made me feel these new sensations. Every occurrence anywhere in the media only further reinforced that impression after that. Later I even took the VHS in my room and wanked while playing the fateful scene over and over.
Fundamentaly, I don't think the scene *gave* me my fetish, it rather feels like it was there all along and that scene was at the right place at the right time. If it hadn't been this one, then another one would surely have produced the same effect.