acting like my crush

I've liked my crush for about 9 months now. And I've (only now) started to act like him a bit. I try to walk a bit like him, steal some quirks in his voice, I smile similarly to him (really big with my teeth showing) and I make the same kind of eye contact as him. And I even steal some of his personality traits. This happens at most when he's not in school. Or when he's not in my class. Why is this?