If you have a homebrew-enabled DS, you may want to draw pictures on it. You may not, obviously, but on the off chance, take a look at this free Colors! app.
“Colors! is a simplistic digital painting application for Nintendo DS based on modern painting-techniques developed for drawing tablets in programs like Photoshop,” said whoever made it. “By taking advantage of the pressure sensitivity of the DS touch-screen it becomes a perfect portable digital sketch-book.”
You can paint virtual cats. And that should be reason enough to try it.