Fucking crack when?
Spline, a 2D animation program
Err, meant Spine
All you have to do is make a simple 3D mesh that only works from 1 viewpoint with this planar mapped onto it. Basically just raise the thigh and face areas, and a cube shape for the gun, and twist those regions during animation so they warp in a realistic fashion.
I'm not sure why you would need this program to accomplish what that video shows. Just make a 2D rig in whatever 3D software you usually rig in.
More animations with characters that move like fucking seaweed.
it's literally building a 3D mesh and using it as a 2D plane. Nothing beats handpainted flat color 3d models when it comes to stylish animations and characters.
This tweening shit will never look good.
when you think you're ready.