Autodesk has been rapidly adding apps to their free suite of consumer 3D apps, with the most recent addition being 123D Creature, with which you can create "creatures".
The USD$7.99 iOS app is similar to others in the suite, permitting easy generation of a 3D model. This app is focused on limb-based objects that will become amazing creatures, unlike our rudimentary attempt shown here.
The creation process proceeds through a series of steps where you gradually build up the model, beginning with the basic armature, then filling out the limbs, and so on.
When you're done you can export the mesh for 3D printing or if you'd like to a 3D print service like Sculpteo. Sculpteo's CEO, Clément Moreau told us:
This app is really amazing, and contains the 3d printing cloud engine feature from Sculpteo.
We agree - it's a fantastic app for creating creatures.