(obsessive interest in or enthusiasm for a subject, typically one of specialist or minority interest).
Occasionally I like to paint things that are just ridiculous or totally nerdy. My studio time is pretty limited these days, so most of these are older paintings (read: pre-kid). It might be an eventual goal to make art time consistent enough that I can do some more of this kind of thing though. Painting details of something like a creeper from Minecraft just totally cracks me up and also happens to be super fun.