  The microscopic spectral density of the Wilson Dirac operator for two flavor
lattice QCD is analyzed. The computation includes the leading order a^2
corrections of the chiral Lagrangian in the microscopic limit. The result is
used to demonstrate how the Sharpe-Singleton first order scenario is realized
in terms of the eigenvalues of the Wilson Dirac operator. We show that the
Sharpe-Singleton scenario only takes place in the theory with dynamical
fermions whereas the Aoki phase can be realized in the quenched as well as the
unquenched theory. Moreover, we give constraints imposed by gamma_5-Hermiticity
on the additional low energy constants of Wilson chiral perturbation theory.
