Hot Topic Sizes

Ok, so this confuses me. Everywhere I go, I buy medium sized clothes. sometimes I can even get a small, though very rarely. But when I go to Hot Topic, I have to get a large for it to fit me like a medium usually does. So are their clothes built for little anorexics, or are they just meant to be super tight? I have no idea, but this is a question for anyone out there to answer. Please, I need to know. If I go to Rue21, I get a medium, if I go to Aeropostale, or American Eagle, or even Walmart. Hot Topic is the only place I ever get a large. Why??????????????????? Oh, I got a Slytherin shirt on clearance there today... =)