  The measurement of the anomalous magnetic moment of the muon provides a
stringent test of the standard model and of any physics that lies beyond it.
There is currently a deviation of $3.1\sigma$ between the standard model
prediction for the muon's anomalous magnetic moment and its experimental value.
We calculate the contribution to the anomalous magnetic moment in theories
where the muon couples to a particle in a hidden sector (that is, uncharged
under the standard model) and a connector (which has nontrivial standard model
gauge and hidden sector quantum numbers).
