It's been suggested to me, but I haven't looked into it. I think I'd need to improve both my technique and my equipment -- at the moment I've only got a basic hobbyist's sewing machine, and it's not intended for heavy-duty work and has limited features. I'd probably need to get a serger; some of the seams in that penguin's jacket were "finished" with glue.

Given my relatively limited expenses, I could probably make a living by doing so, but I'm a bit reluctant to turn a fun hobby (which I can do whenever I feel like it) into an income source (which would imply commitments).