Gravity Based Stretching of Half of Model

I'm modelling a Wiener Dog in 3D and Creating a 2D Sprite. Im trying to figure out how when the dog walks off of whatever is higher than ground level his body stretches until his front half hits ground and then his rear catches up (Slingshot effect, Slinky, Etc...). I'm trying to achieve this in both 3D and 2D as a learning experience and it makes me giggle.

Any help would be much appreciated.