This is my tribute to the twisted mind of Steven Colbert. It is also a decidedly creepier derivative of http://www.thingiverse.com/thing:6291. Print, assemble, and twist Colbert's head to your heart's content.
Instructions are the same as for http://www.thingiverse.com/thing:6291. I've heard this can be scaled up by about 1.7 times, using M5 screws instead of M3. You have may to drill out the holes a little, since calibration can easily change hole size.
Colberthead.stl is included because it's called by headgears.scad. It's a centered and decimated version. The assembly.stl file is just there for reference to help put it together. If you want to see the gears spin, compile assembly.scad (it's made for animated viewing). It loads quickly because it doesn't do any operations.