Way back when Kevin and I first started going to comic conventions and store signings, we quickly learned that quite a few people wanted more than our quickie Turtle head sketches -- they wanted full TMNT sketches (more people, in fact, than we usually had time to accommodate). So for a few years we started doing sketches before going to shows so we would have some ready for those fans. We each did quite a few of these, and made copies of a lot of them. They were usually portraits of one of the Turtles, though occasionally we did group shots. Sometimes we even collaborated on these sketches, one of us penciling and the other inking.
Here's one of mine from 1986, a shot of Donatello on a rooftop, with what I suppose is the moon behind him.
These days, I rarely do drawings like this at shows, simply because I have learned through experience that doing so almost invariably leads to a complete logjam, with most people wanting a drawing leaving the show with nothing. So I have compromised by doing slightly more elaborate head sketches, which I am able to do just fast enough to keep up with demand. I also charge significantly less for them than I would for full-figure sketches. -- PL