  The Teukolsky Master Equation describes the dynamics of massless fields with
spin on a Kerr black hole. Under separation of variables, spin-reversal for
this equation is accomplished through the so-called Teukolsky--Starobinsky
identities. These identities are associated to the so-called
Teukolsky--Starobinsky constants, which are spin-dependent.
  We collect some properties of the Teukolsky--Starobinsky constants and dispel
some myths present in the literature. We show that, contrary to popular belief,
these constants can be negative for spin larger than 2. Such fields thus
exhibit a novel form of energy amplification which occurs for non-superradiant
frequencies.
