So I recently setup my forums with account associations to ease the registration process for new people (Facebook Twitter and Google+). I tested this with trying to create a new accout using a dummy Google plus account I have lying around. This results in the following screen: So far so good, does exactly what I want which is still asking a desired username for the forum itself. I'm using a regex expression [a-zA-Z0-9_] to validate the username (which is the same requirements for a minecraft username). However, people still somehow manage to register with their real names, despite of the regex. I'm talking stuff like Joe Smith or Oscar Johanssen. Obviously these names shouldn't be expected with the current regex. So how does this actually happen?