We present an axiomatization of a problem in commonsense reasoning, characterizing the proper procedure for cracking an egg and transferring its contents to a bowl. The axiomatization is mid-sized, larger than toy problems such as the Yale Shooting Problem or the Suitcase Problem, but much smaller than the comprehensive axiomatizations associated with CYC and HPKB. This size of axiomatization permits the development of non-trivial, reusable core theories of commonsense reasoning, acts as a testbed for existing theories of commonsense reasoning, and (...) encourages the discovery of new problems in commonsense reasoning.We present portions of core theories of containment, falling, and pouring, integrated into Shanahan's circumscriptive event calculus, and show how these can serve as the basis of an axiomatization that partly characterizes egg cracking. We discuss several commonsense reasoning problems encountered during this research, such as the Initial Specification Problem (a relative of the frame problem that occurs in theories in which fluents can trigger actions), and the Unobtainable State Problem (the problem of determining whether or not a theorem stating that one cannot get from one state to another is meaningful). (shrink)