Illustration assignment, wherein we were to draw an interior space with an "unexpected object". We could use pencil or ink.
I had nothing. Absolutely nothing. Then I suddenly thought, hey, what if there was a random ink-blot on a page of pencil? Eh...no, I'd have to draw humans reacting to that, and that's eh...
Wait! Got it! Monster underneath my bed!
Given the fact that I gave up on dip-pens really quick and shoved them under my bed, this scenario seems entirely plausible.