In set theory, one comes across the notion of "vacuous truth." A statement is vacuously true if it is true but does not quite say anything. The structure of a vacuously true statement is typically of the form: everything with property A also has property B, with the caveat being that there is nothing in property A. For instance one could say: all humans with gills are sharks. This statement is vacuously true because there are no humans with gills. It is natural to dismiss such examples as absurd and pathologies within the framework of set theory. However the notion of vacuous truth arises in some pedagogical situations. The reader is undoubtedly curious whether a situation requiring the examination of "vacuous" truth can arise in a contemporary mathematics classroom. In fact such situations do arise. In this article, the author describes one such situation in a preservice elementary mathematics classroom. This unusual set-theoretic pedagogical situation is known as Cantonian conundrums. (Contains 1 footnote.)