Back in 2006, just before I turned 14, my mom was still iffy when it came to online forums, so I didn't really surf the web too much. Since it was Pokémon-related, she was more accepting of it, but I still had help signing up (Serebii really and truly is the first website I became a member of, and I was just that inexperienced when it came to joining things). I had to come up with a name quickly, and being a 13-going-on-14-yar-old, I couldn't be creative. Purposefully misspelling "cutie" with a "K" was as creative as I got at the time (I would've gone for Lil' Purple Bird or just Lil' Bird, but I didn't really want to use my old e-mail name at the time).
It stuck since. I haven't had the heart to change it, and "KP" rolls off the tongue.