  Planets are often invoked as the cause of inferred gaps or inner clearings in
transition disks. These putative planets would interact with the remnant
circumstellar disk, accreting gas and generating substantial luminosity. Here I
explore the expected appearance of accreting protoplanets at a range of
evolutionary states. I compare synthetic spectral energy distributions with the
handful of claimed detections of substellar-mass companions in transition
disks. While observed fluxes of candidate companions are generally compatible
with accreting protoplanets, challenges remain in reconciling the extended
structure inferred in observed objects with the compact emission expected from
protoplanets or circumplanetary disks. I argue that a large fraction of
transition disks should harbor bright protoplanets, and that more may be
detected as larger telescopes open up additional parameter space.
