This is what happens when you play with non-newtonian liquids. In this case, corn starch and water. I didn't know what they were either, Wikipedia has this to say:
A non-Newtonian fluid is a fluid which cannot be described by a single constant viscosity. Most commonly, the viscosity changes with the applied shear stress. Many polymer solutions and molten polymers are non-Newtonian fluids.
I just thought the video is cool.