  Two classical novae V1493 Aql and V2362 Cyg were known to exhibit
unprecedented large-amplitude rebrightening during the late stage of their
evolution. We analyzed common properties in these two light curves. We show
that these unusual light curves are very well expressed by a combination of
power-law decline, omnipresent in fast novae, and exponential brightening. We
propose a schematic interpretation of the properties common to these
rebrightenings can be a consequence of a shock resulting from a secondary
ejection and its breakout in the optically thick nova winds. This
interpretation has an advantage in explaining the rapid fading following the
rebrightening and the subsequent evolution of the light curve. The exponential
rise might reflect emerging light from the shock front, analogous to a
radiative precursor in a supernova shock breakout. The consequence of such a
shock in the nova wind potentially explains many kinds of unusual phenomena in
novae including early-stage variations and potentially dust formation.
