I use my username, Fox-Trot-9, b/c it's what I've been using for years now. I love nine-tailed foxes, not the big scary kind from Naruto, but the small and fluffy kind that you could keep in your house as a pet. And no, I did not come up with that username b/c of that "What Does the Fox Say?" song or that animatronic nightmare fuel that jump scares you in Five Nights at Freddy's.
As for my current avatar, she's Yandere-chan from Yandere Simulator. I chose that as my avatar, b/c Markiplier's let's play vids of that game are so damn funny, and sometimes I feel a bit 'stabby' myself (a la, Markiplier's 'butt-stabber' phase).