  We consider the contributions to $g_\mu-2$ from fourth generation neutral and
charged leptons, $N$ and $E$, at the one-loop level. Diagramatically, there are
two types of contributions: boson-boson-$N$, and $E$-$E$-boson in the loop
diagram. In general, the effect from $N$ is suppressed by off-diagonal PMNS
matrix element $V_{N\mu}$, from the Standard Model to the Two-Higgs Doublet
Models. With contribution from $E$, we consider flavor changing neutral
couplings.
