  We introduce a manifestly little group covariant on-shell superspace for
massive particles in four dimensions using the massive spinor helicity
formalism. This enables us to construct massive on-shell superfields and fully
utilize on-shell symmetry considerations to derive all possible $\mathcal{N}=1$
three-particle amplitudes for particles of spin as high as one, as well as some
simple amplitudes for particles of any spin. Throughout, the conceptual and
computational simplicity of this approach is exhibited.
