Because of the top quark's very large mass, about 175~GeV, it now provides the best window into flavor physics. Thus, pair--production of top quarks at the Tevatron Collider is the most incisive probe of this physics until the Large Hadron Collider turns on in the next century. In this talk I discuss how moments of the t ̄t invariant mass distribution can be used to distinguish among standard and alternative mechanisms of t ̄t production.First author draf