Marvin with Improved Crotch

This is the classic [3D Hubs Marvin keychain](https://www.thingiverse.com/thing:215703) with some minimal improvements. This is one of my favorite printing tests because it has some challenging parts, but I noticed that the prints always had a little curl between the legs. This is because the original model, being constructed from a sphere shape, has an actual overhang there. Unless you would print with supports, this results in one or more circles being printed in thin air. I modified this part of the model so the overhanging zone is replaced by a bridge, making it perfectly printable without supports.
I also made a small adjustment to the little overhang between the eyes, because that was another problematic part, it required a horizontal line to be printed with one end anchored to nothing.