  New Physics models in which the Standard Model particle content is enlarged
via the addition of sterile fermions remain among the most minimal and yet most
appealing constructions, particularly since these states are present as
building blocks of numerous mechanisms of neutrino mass generation. Should the
new sterile states have non-negligible mixings to the active (light) neutrinos,
and if they are not excessively heavy, one expects important contributions to
numerous high-intensity observables, among them charged lepton flavour
violating muon decays and transitions, and lepton electric dipole moments. We
briefly review the prospects of these minimal SM extensions to several of the
latter observables, considering both simple extensions and complete models of
neutrino mass generation. We emphasise the existing synergy between different
observables at the Intensity Frontier, which will be crucial in unveiling the
new model at work.
