  If planetary systems are ubiquitous then a fraction of stars should possess a
transiting planet when being microlensed. This paper presents a study of the
influence of such planets on microlensing light curves. For the giant planets
recently identified, the deviations in the light curve can be substantial,
although the specifics of the perturbations are dependent upon the radius of
the planet relative to that of the star, the location of the planet over the
stellar surface and the orientation of the sweeping caustic. Given that the
instantaneous probability of transiting hot-Jupiter like planets is small, less
than a percent, and only a proportion of microlensing events exhibit caustic
crossing events, the probability of detecting a transiting planet during a
microlensing event is small, $\sim10^{-6}$. However, a number of factors
influencing this probability, such as the number of solar type star that
possess planets, are uncertain, and the prospect of detecting transiting
planets in future large catalogues of microlensing light curves may be viable.
The results of this study also have bearing on the gravitational microlensing
of spots on the stellar surface.
