Someone posted some Go!Go!7188 videos on a music video newsgroup a few years back. I liked the songs but thought nothing of it. From there, someone gave me some X-Japan, but again I thought nothing of it. Then someone posted Morning Musume's Hawaiian Singles Collection, and I got it and listened to a few songs, but then forgot all about it.
Finally I was browsing through Google Videos when videos of Ayaka's Surprise English Lessons began cropping up, subtitled by SMP. I watched them, thought they were funny... things clicked, I started listening to the things I had downloaded before, and it just snowballed from there