Exactly…hard to say.
Generaly…with a fluid simulation.
Nice! Really nice! I guess he modeled the Snowman, then used that as an obstacle for his fluid simulation and put an Inflow into the Snowmans head. than, after the snowman was filled, the first simulation ended and he converted the dublicated the result and turned it into a mesh (alt+C) and used a Softbody simulation on it! Then, after that, he dublicated the result again and used it as the fluid for the 3rd simulation and for the change in Gravity he probably also used the resulting mesh on a 4th simulation with the difference that the domains gravity was changed!
Thats my guess at least… I tried to reproduce this, but Blender kept crashing
Very nice Idea though!
That’s my guess somewhat, him doing several simulation seperately. Is the snowman collapse one of the new cvs soft bodies features?