A bit o' fanart inspired by Grant Morrison & Darick Robertson's comic, "Happy!".
I don't think it's giving away too much to say that the protagonist of the comic is suffering from some pretty heavy mental and physical damage, and one of the issues he contends with is Happy, the self-proclaimed imaginary horse. So, clearly, this drawing had to happen.
"Oh, I'm about 1-2-3-4-5 grades above a hallucination, Nick."