Meet Cheeming Boey.  He draws on Styrofoam cups with a Sharpie.

Here is a section of an interview he recently did:

Q: How did you come up with the idea?

Boey: I had no paper while I was craving to sketch one day outside a coffee shop, saw a cup on top of a trash can, took it and started drawing on the surface. I had forgotten how well ink flows on the Styrofoam surface. Its got a completely different feel from paper. Initially it was just with a ball point pen, I later moved to sharpie because I had some sharpies on my desk at work.

Q:  Tell us about some of your favorite designs.  Why do they resonate with you?

Boey: I like the ones that are more personal, like a dining experience with a friend over sake and stories. I also like waves; hence a lot of my cups have a spaghetti-like, wave motif to it. One of my favorite Japanese artists who has influenced me heavily is Hokusai, and I think a lot about how he draws his waves when I draw mine.

Q: What is the longest amount of time you have spent on one cup?

Boey: 3 months. I don’t do initial drafts on the cups, so what you see is on the final product is the first pass. It takes forever to work on an elaborate piece because my next line could completely ruin the composition. Or I get nervous about drawing certain shapes. Or poses.

So sometimes I take hours to figure out the composition in my head, sometimes I don’t come back to it for months.
I have to also make sure the foam cups are absolutely lint/ hair free. They charge up easily and tiny hairs or lint can stick to it. And when the fine point on the sharpie catches one of these hairs, a thin line can suddenly become a broad stroke. Terrible.