How to make an Object Flop?

I want to make it so when pressing w, a, s, or d and then space the character will flop in that direction. It sounds like it could be difficult so anything similar would be great. I'm also new with animating so some pointers would be appreciated.

 

Video tape yourself flopping around for reference. Animate the flopping using the reference. Export the animation flopping. Import into Unity.

Game done.

In all seriousness though. You need to be more descriptive of what you are asking for. How to create a flop animation? How to set up the statemachines? What scripting do I need to get this mapped to my controller?