The singleton is a remarkable unitary representation of the conformal algebra, which was first investigated by Dirac in the sixties, and whose bulk/boundary description in the seventies by Flato and Fronsdal is sometimes considered as a precursor of the AdS/CFT correspondence. The flat limit of the singleton on AdS spacetime is shown to provide the bulk dual, in Minkowski spacetime, of the Carrollian conformal scalar field living at null infinity.