abstract: “Slice regular functions” are the quaternionic analog to what holo-morphic functions are over the complex numbers. The classical Pi-card Theorem states that for a non-constant holomorphic function f : C → C the image avoids at most one point. This raises the question: How many points may be avoided by a non-constant slice regular function F : H → H? We show that there is no bound on the cardinality of H \ F(H). Instead there is a bound on the dimension of the affine hull of H \ F(H).