Non-Newtonian Fluid
In one episode of the Big Bang Theory (season 2) Sheldon et al. poured a bowl of starch mud on a subwoofer then turned on the music. The starch mud danced with the rhythm of the vibration with changing shapes, like a pudding. Sheldon showed off this scene to Penny as an example of a non-Newtonian fluid, which as usual was not appreciated by Penny.
In fact, Newton was not in good relationship with his contemporary counterpart Hooke. This is even obvious in rheology: While Newton set up the ideal end of viscous fluid (Newtonian fluid), Hooke described the other opposite, the ideal elastic solid (Hookian solid). All the stuffs in the world belong to certain places between these two limits, and thus are more or less viscoelastic. Therefore, by "non-Newtonian" Sheldon could only mean "more Hookian" because it is the only other end. And indeed the starch mud did exhibit some shape and motion that characterize elasticity, under, of course, the special condition on the subwoofer. It can even withstand human weight, as evidenced by the following video.
It has long been a tradition that the equations of Newtonian viscous flow and Hookian elasticity be both linearly combined to simulate the whole spectrum of viscoelasticity in between. The corresponding theoretical framework is thus called linear viscoelasticity. However it is also found that in even more situations stuffs deviate from linear viscoelastic spectrum, especially under large deformation or deformation rate. Although we can likewise call the whole phenomenon nonlinear viscoelasticity, there is no universal theory or explanation.