I've used tinythinker as my internet handle for a loooong time. Not all accounts using tinythinker are me anymore, but that's not a problem as you can kind of sort the ones that fit with academic themes, societal issues, sci-fi fantasy, and video games from the rest.
Originally I used a handle from a chatroom called Moe's Tavern that was taken from a book, and sometimes a character I made on a social MMO, but when I ventured into message boards I wanted something else.
The first message board I decided to try was (and still is as of this writing) called CARM. Someone there had gone with the name "Pinky" and used an image of a cartoon character of the same name for the account. I thought about using "The Brain", but I knew I might not always control my image/avatar so people might get the wrong idea. After considering it and pondering some other diminutive genius characters, I just went with tinythinker.
I knew some people would use it to mock me by interpreting it as suggesting I am stupid, but I figured, let them. Being underestimated on message boards, chats, etc. where people debate and discuss sensitive topics can be an advantage, and helping rude people self-identify is a bonus.