  Charged lepton mixing as a consequence of neutrino mixing is studied for two
generations $e,\mu$ in the temperature regime $m_\mu \ll T \ll M_W$ in the
early Universe. We state the general criteria for charged lepton mixing,
critically reexamine aspects of neutrino equilibration and provide arguments to
suggest that neutrinos may equilibrate as mass eigenstates in the temperature
regime \emph{prior} to flavor equalization. We assume this to be the case, and
that neutrino mass eigenstates are in equilibrium with different chemical
potentials. Charged lepton self-energies are obtained to leading order in the
electromagnetic and weak interactions. The upper bounds on the neutrino
asymmetry parameters from CMB and BBN without oscillations, combined with the
fit to the solar and KamLAND data for the neutrino mixing angle, suggest that
for the two generation case there is resonant \emph{charged lepton} mixing in
the temperature range $T \sim 5 \mathrm{GeV}$. In this range the charged lepton
oscillation frequency is of the same order as the electromagnetic damping rate.
