Most Helpful Guy
copying is the highest form of flattery. The guy most likely likes you and is unsure how to act so he copies you. That or he is just doing it to mess with you. If he is laughing a lot then he is just messing around.
Most Helpful Girl
its the mirror affect. if you brush your tips with your cheek and he does the same; most likely he isn't aware he's doing it but it shows he has strong feelings towards you