We report the results of an experimental investigation into buckling in elastic and plastic cellular materials under dynamic compression. The buckling instabilities are in the form of a global pattern switch where the square array of circular holes is transformed into a set of orthogonal ellipses. Properties of the instabilities in the elastic and plastic cellular materials are compared and contrasted. The case of the elastic structure is considered as a delayed pitchfork bifurcation. On the other hand, the response of the plastic lattice is complex, and an irreversible global instability is only found above a critical compression rate.