Well, back when I first played pokemon White, I nicknamed every pokemon I caught, including legendaries. So when I got to the point of Catching Zekrom, I neamed it after the only black dragon I could think of at the time, the dragon owned by Galbatorix in Eragon, Shruikan. It wouldn't have made any difference normally, but the next day the pokemon global link was finally set up, and I needed a username for it. All the ones I used at the time had already been taken, so I tried to think of a more obscure name, and my Zekrom's nickname came back to me. From then on it's been my go-to username pretty much everywhere.