It all started as a commission for a cartoon series where astronomy was explained with sheeps. No further details, stylistic choices nor anything else was given. So, I had to make everything from scratch, and I started by finding a style for the sheeps!
After sketching them, and drawing final models in a vector graphics program, I faced the problem of vehicles: in this series there had to be various vechicles, all seen from different angles in the same episode, and it was planned to add often new ones. So I decided that the easiest route would have been to make 3D models for them, and render them shadeless, to give the same look as the rest of the drawings.