Several years ago, Rabbi Joseph Soloveitchik (a.k.a. the Rav) ruled that toothpaste is not "fit for a dog to eat" and therefore can be consumed on Passover without special rabbinic certification. After hearing this in class, a student raised his hand and stated that the prior night he had conducted an experiment, leaving an open tube of toothpaste by his dog's bowl. The next morning, the toothpaste was gone, seemingly disproving Soloveitchik's theory. The Rav simply responded, "Your dog is crazy."