  Extended material at large radii surrounding a supernova can result in a
double-peaked light curve. This occurs when the material is sufficiently
massive that the supernova shock continues to propagate into it and
sufficiently extended that it produces a bright first peak. Such material can
be the leftover, low-mass envelope of a star that has been highly stripped, the
mass associated with a wind, or perhaps mass surrounding the progenitor due to
some type of pre-explosion activity. I summarize the conditions necessary for
such a light curve to occur, describe what can be learned about the extended
material from the light curve shape, and provide an analytic model for fitting
the first peak in these double-peaked supernovae. This is applied to the
specific case of a Type Ic super-luminous supernova, LSQ14bdq. The mass in the
extended material around this explosion's progenitor is measured to be small,
~0.3-0.5 Msun. The radius of this material can be ~500-5000 Rsun, but it is
difficult to constrain due to a degeneracy between radius and the supernova's
energy. In the future, spectra taken during the first peak will be important
for measuring the velocity and composition of the extended material so that
this degeneracy can be overcome.
