My pet rock just sits there..doing nothing..but peeing on the floor.
Actually, sadly I do not have a pet, but when I was in Spain with my best friend, we had her dog with us, and he LOVES the sound of a guitar. So every time I started playing, he started smiling 'n looking at me, and when I stopped he was like: "Pff! Arsehole! I'm goin to look somewhere else now, until you start playing again"
I love animal reactions to music