My username is based off my middle name, which is Skye. 42 is one of my favourite numbers, and is also a reference to A Hitchhiker's Guide to The Galaxy as 42 is the answer to the ultimate question of life, the universe, and everything. Put the two together and BAM! You have yourself a somewhat decent username.
Also, the reason for their being a hyphen between the two is because of my DeviantART account. When I signed up, someone already had the username Skye42, so I then changed it to Skye-42. Depending on the site, depends how I write it.
...Fun fact, I used to called Derp-a-licious on Steam because I'm just so Derpy... Good thing you can change your name on Steam...