1. Why did you become interested in Sonic?
2. How did you hear about Sonic?
3. How long have you been a Sonic fan?
This sort of answers all three, but seeing an episode of Sonic X on Saturday morning 4kids when I was 8 or so! I believe it was the season 3 ice planet episode? I was just 'huh, this looks cool but I don't have any context for it, I'll look up 'sonic cartoon' on youtube.' Then I found AoSTH and Satam (which had entire episodes posted either in their entirety or in 3 parts in fairly high quality) and thought they were really cool/funny, and after that I've never fully left.
One of the first books I learned to read on was this one too so that was when I was three or four, although that's long since been donated, and I was sort of confused watching Aosth with 'where is Sally?', pfft. (I knew X was its own thing, but I didn't realize Aosth and Satam were separate at the start bc they had more similar art styles, at least to my kid-eyes.)