  The 4d Kerr geometry displays many wonderful relations with quantum world
and, in particular, with superstring theory. The lightlike structure of fields
near the Kerr singular ring is similar to the structure of Sen solution for a
closed heterotic string. Another string, open and complex, appears in the
complex representation of the Kerr geometry initiated by Lind and Newman .
Combination of these strings forms a membrane source of the Kerr geometry which
is parallel to the string/M-theory unification. In this paper we give one more
evidence of this relationship, emergence of the Calabi-Yau twofold (K3 surface)
in twistorial structure of the Kerr geometry as a consequence of the Kerr
theorem. Finally, we indicate that the Kerr stringy system may correspond to a
complex embedding of the critical N=2 superstring.
