Yes, I remember exactly. It was in 2005. My co-worker had lent me the series to keep me amused because I was home sick for two weeks. The precise moment was 20 minutes into Welcome to the Hellmouth. I think I literally called me mother, and something like this to her, "This is my new favorite show, Mom. I am going to love it forever. It's about this girl, who's funny and cute, and she slays vampires with her friends, and it's clever and smart..."
I knew right away Buffy was something special. I had never seen anything like it. I completely fell in love with it.
Yesterday, I was watching School Hard, and I was thinking about Buffy and Spike, and said to myself that I have never loved two characters so much as I do these two. It's truly unhealthy.