Physics based animation

I recently came across this twitter account about physics based animation in unity:
https://twitter.com/punchesbears

I was just wondering, where do you even begin to do animation like this? It looks as if the animations are sort of controlled by physics (like ragdoll animation is), but there also must be some element of defining keyframes.

If anyone could point me to tutorials or resources of any kind that can describe how this is done, that would be awesome. Thanks!

P.S. I've been googling around a while and haven't found anything like this (though maybe I'm not searching for the right things)

 

Does this help? http://docs.unity3d.com/Manual/wizard-RagdollWizard.html

 

http://forum.unity3d.com/threads/puppetmaster-advanced-character-physics-tool.358445/