endorphin is the industry's first Dynamic Motion Synthesis software.At the heart of endorphin are its Adaptive Behaviours, which - unlike animation data - are completely interactive. With Adaptive Behaviours, 3D characters essentially animate themselves. Move two Football players close to each other and one will automatically tackle the other one, realistically trying to grab hold of his legs and bringing him down .
Or not. It really is up to you. endorphin allows animators to direct scenes in real-time in a way they have never been able to do before. You can change parameters or change behaviours and see the results instantly on the screen in front of you. When you're done, export animation data in one of the many formats, ready for use in your game or VFX shot.

See the demo here:
http://www.naturalmotion.com/endorphin.htm

It is a very expensive product at this time. Something like 10k for commercial license. I hope they will soon imlement something like this in Motion Builder. Overall, I have not understood what this software has that Massive does not have.