  Heun-type exact solutions emerge for both the radial and the angular
equations for the case of a scalar particle coupled to the zero mass limit of
both the Kerr and Kerr-(anti)de-Sitter spacetime. Since any type D metric has
Heun-type solutions, it is interesting that this property is retained in the
zero mass case. This work further refutes the claims that $M$ going to zero
limit of the Kerr metric is both locally and globally the same as the Minkowski
metric.
