Many creatures navigate their world through undulation – the unidirectional propagation of bending waves along the body. Undulatory locomotion in a fluid is well studied, at least at low Reynolds number. There, undulation breaks time-reversal symmetry and an organism can locomote by using the anisotropy of fluid drag with respect to body shape. On land, limbless creatures such as snakes also use undulation to traverse "featureless" surfaces with relative ease. I will discuss theoretical models and experimental observations that illustrate how snakes accomplish this by using the frictional anisotropy provided their scales, as well as selective body lifting. To provide another example of an undulator in action, I will discuss some recent modeling and experiments that show how swimming nematodes interact with microfluidic environments filled with immovable obstacles.