Mine may look simple but it had a story behind it.
Back when I was about to join my first Pokemon forum, I was trying to find the perfect username and after discovering my love towards Dawn, whose Japanese name is Hikari, I went with that cos Pokemon is a Japanese franchise, and I needed a Japanese username.
In fact, I think Hikari is one of the cutest Japanese names ever and I like how it sounds. My fave Japanese name for a reason.
However, I knew there was already a "Hikari" here so here's where the numbers came in.
Why 10? Well, I was born in October of 1992, and October is the 10th month in your average calendar year. It's also a number that looks cute on me for some odd reason and it sounds so awesome and catchy and easy to remember. Also, it's one of my fave numbers.
So I combined the two and Hikari10 was the result. I even use this name on other forums I'm on, and if I could change away from this username I'd probably say no.