  Nonlinear supersymmetry is characterized by supercharges to be higher order
in bosonic momenta of a system, and thus has a nature of a hidden symmetry. We
review some aspects of nonlinear supersymmetry and related to it exotic
supersymmetry and nonlinear superconformal symmetry. Examples of
reflectionless, finite-gap and perfectly invisible PT-symmetric zero-gap
systems, as well as rational deformations of the quantum harmonic oscillator
and conformal mechanics, are considered, in which such symmetries are realized.
