I looked through several tutorials before I started, and it seems the best idea would have been to use an oil based Sharpie paint marker. I don't have paint markers, and someone else had said the regular black ones work fine, so that's what I used. I drew the cats on the mug and followed the baking instructions (put cold mug in cold oven, heat to 350 for 30 minutes, then let sit in the oven and cool off until oven is cool).
I wanted to play with the cats in watercolor as well, so I grabbed a little watercolor postcard and got to work.
Unfortunately, I'm having trouble trying to rotate this properly, but you get the idea. I like the cats much better solidly filled in. But this was the point of this weekend, to doodle and play with no high expectations of masterpieces.