This post used to be on Posterous. I rescued my posts before Posterous shut down and am now sharing them here.
The Unicorn version came out a little messed up due to my sizing the file wrong - the pen went off the edge of my sticky note pad and mussed everything up. I resized the plot to fit the sticky note fine, but had some pen registration issues with the now-crumpled sticky note pad. I'll probably try this again later with some nicer stock.
New files and more detailed description over on Thingiverse.