Edit, 15 November 2012: I'm honored that the Winter 2013 Make: 3D PRINTER BUYERS GUIDE mentioned the Roll-A-Hedgehog (p20, illustrated on p2))... but I very strongly urge you NOT to use this as an infant toy unless you are paying very close attention. The body, if printed without scaling, is borderline large enough for safety. The wheels/axles, however, would definitely be choking hazards if they were to break. I've not had one break yet, but it's not impossible: that's a cross-layer feature.
Just a little hedgehog, rollin' along.
Thanks to everyone who test printed before I had a chance to do so. With your feedback, my first print of this rolled great!
By the way, the hedgehog profile was borrowed from a wood ramp walking hedgehog my parents brought back from a trip to the Czeck Republic. I'd like to render that printable too.
Print and play!
I printed without acceleration, 15% fill, 0 extra shells. Less fill would probably still be plenty sturdy.
Note that my rendering is misleading: this is not set up for dualstrusion yet. I suppose with the right software you could extract the bodies and save separately?
Take precautions to preserve exterior surface finish: at this scale (~44mm long) there is a consistent 0.7mm gap between wheels and body. Any blobbing or such surface artifacts risks bridging that gap.
Using the scale function to increase overall size will increase this gap proportionally... but he'll be less cute.