I've seen quite a few of these humanoid creatures around the internet:
How do I go about making one of these? Can I make a basic model from cylindrical sections for each joint and then rotate them according to the action?
Those images are not created via Illustrator. You need a real, live, 3D application to create such scenes. Illustrator's 3D abilities are severely limited.
If you really want to try in Illustrator, you need to be very familiar with the Gradient Mesh Tool and be very patient when creating.