In case you are wondering, a Non-Newtonian fluid is one that can temporarily exhibit the behavior of a solid. This occurs when there is a rapid application of force on the fluid at which time it exhibits what is called “shear thickening,” which is to say it appears to be solid. The rapidity of the application of force is critical. If you slowly apply force it will behave as one would expect, which is to say: as a fluid. Here is a fun demonstration.
In short, you too can have fun with Non-Newtonian Fluids. Corn starch and water is all you need. Read more about this at Wikipedia.