This paper investigates the use of discrete couplings in series elastic actuation in order to increase variability of dynamic legged robot locomotion. The couplings are capable of engaging and disengaging the connection between an actuation element and a mechanical spring in real time such that the series elasticity could be used to load, store and retain energy, and release it in the necessary timings. Such a mechanism is particularly beneficial for hopping or running locomotion, because it allows preloading of spring in flight phase. Through a series of simulated and physical robot experiments, this paper explains how such variability of actuation dynamics can improve performance of hopping locomotion under the limitation of actuator forces, as well as the controllability of behaviors. Compared to the conventional hopping robots, the proposed control strategy makes locomotion robots capable of higher hopping without larger actuation forces, and changing behaviors for more aggressive manoeuvres.