  In this article, we consider some Carrollian dynamical systems as effective
models on null hypersurfaces in a Lorentzian spacetime. We show that we can
realize Carroll models from more usual ``relativistic'' theories. In
particular, we show how ambient null geodesics imply the classical ``no Carroll
motion'' and, more interestingly, we find that the ambient model of chiral
fermions implies Hall motion on null hypersurfaces, in agreement with previous
intrinsic Carroll results. We also show how Wigner-Souriau translations imply
(apparent) Carroll motion, and how ambient particles with a non vanishing
gyromagnetic ratio cannot have a Carrollian description.
