Lyric discussion by Lyswan 

Cover art for Lilly lyrics by Pink Martini

I always thought it was about a foolish girl, she's not really mean, it's just that she loves having fun and doesn't care about anything much. It could be about a dog, but why would a guy come back to live with his mother just because he's lost his dog? That would be too much, wouldn't it? Or, maybe the songwriter made it ambiguous on purpose.