Nerd. One whose unbridled passion for something defines who they are as a person, without fear of other people's judgment.
As far as being an actor is concerned, you have to have passion. If you're not bringing the passion of the character into the room with you, you might as well not come into the room at all.
To do panels where you get to interact with your fans, in a really intimate, awesome way, and to let them ask all of the questions, is fun to me and it shows them that you care about their opinions, their thoughts, and their passion for your project.