Yesterday, while I was out walking with my dad, I saw a sign that said "Circa" and thought "Cirno."
There was another thing, but I forgot it. :x
EDIT: Also, just now, someone mentioned Kazama from Tekken. I thought "Yuka Kazama."
EDITEDIT: Also, you know you're addicted to Touhou, and that you have a musical mind, when your brain starts mixing up Touhou tunes, i.e. mentally segueing from Strawberry Crisis to Plastic Mind, or from G Free to Ancient Temple.