COY stands for Cross Over Yuri. The premise is pretty simple, I have a list I've compiled of over 500 cute girls from various anime and manga. I then use a random number generator to make pairing, which I then draw. Every third picture is a threesome.
This was a complicated piece. Not because of anything with the image itself, but because I got into quite a tiffle with Gelbooru over it. Apparently, it didn't meet their quality standards because Videl's mouth, quote, "Looks like a Goomba." Whatever. For some reason, their policy against allowing Western artists never came up, though.
Interestingly enough, though, I saw this pic on Gelbooru several months later. It was up for quite a while before someone realized I wasn't Japanese and had it taken down. During that time, it received an extremely high rating and had several very positive comments, probably more than it deserved. Go figure.