Heaps of people copy me, and it's driving me insane! Where has originality gone!?

I seem like a really quiet and shy person, but I'm really outgoing and silly to people that are close to me like my friends and family. I'm also not shy on the internet and on facebook and all that. But people think that just because I'm quiet, they can copy all my phrases and sayings and things. Even my friends copy me, because they know that I'm shy to other people that don't know me.

What should I do!? I can't stand it! Why do people copy me and then go off and pretend they've made it up?