It takes a bit to decide on the desired action and the rest of it is not that complicated - just bunch of modifications of a few frames.
I cant tell for sure - I've done it over a weekend along with other stuff. Roughly 6-8 hours maybe.
I love how it has the exactly right amount of frames! And so dynamic!! 
If it's not a secret, how long does it take you to create such an animation (if you do it himself, not in a collab)?
Hey, how about give him some teeth? Great job overall, no doubt, but he looks kinda old without grin.
COOL!!! Maybe they could make an appearance in Mortal Kombat!
Rage-Jiggle! :)