Well, when I signed up for Smogon.. what, two years ago? I needed a name, and what came to my mind was something along the lines of "HOMG WADUR+FYIER=COOLZORZZZ!!1" Then I decided I needed some letters and numbers (and an underscore, because underscores are pimp), and TEH COOLEREST LETTERS EVAR were X and Z and TEH COOLZOREST NUMBER was 18. Thus, Hydro_Flame XZ18 was born. :D
I'm now trying to get it changed to Mizuumi (BECAUSE HOMG JAPANESE IS TEH AWESOMEZXXZXZXZ18). Though I've gone through a lot of different usernames on a number of websites (a lot of them are picked on a whim only for me to realize later that they're terrible), so I don't know how long I'll be using Mizuumi either. It's actually my newest name, up until now I've been registering to sites as "Kyon-Kun" or "Evolutiation".
BUT YEAH.