  In this paper we develop a theory of stability for $G$-categories (presheaf
of categories on the orbit category of $G$), where $G$ is a finite group. We
give a description of Mackey functors as $G$-commutative monoids exploit it to
characterize $G$-spectra as the $G$-stabilization of $G$-spaces. As an
application of this we provide an alternative proof of a theorem by Guillou and
May. The theory here is developed in the more general setting of orbital
categories.
