The Spitzer Space Telescope is pioneering the exploration of infrared (IR) luminous
transients. In our Spitzer InfraRed Intensive Transients Survey (SPIRITS), we are
conducting a systematic search of 200 nearby galaxies for IR-luminous outbursts that
elude detection in traditional optical surveys. In this talk, I will present two
puzzling discoveries from SPIRITS and discuss open questions and the plans to address
them.
 
SPIRITS has revealed a new class of obscured, red transients with mid-IR luminosities
between novae and supernovae that do not exhibit optical counterparts. We call them
SPRITEs (eSPecially Red Intermediate-luminosity Transient Events). The key to
disentangling the various possible physical origins of SPRITEs is IR spectroscopy, which
can only be obtained with the unprecedented sensitivity of the upcoming James Webb Space
Telescope (JWST). I will discuss possible SPRITE origins and the JWST Guaranteed Time
Observation (GTO) program I am leading to determine their nature.
 
In SPIRITS, we serendipitously discovered variable mid-IR counterparts of ultraluminous
X-ray sources (ULXs). A ULX is an off-nuclear point source showing extreme,
super-Eddington X-ray luminosities thought to be driven by accretion onto a compact
object in a close binary undergoing Roche Lobe overflow. We attribute the mid-IR
emission to a circumbinary dust disk produced by the outflow from the supergiant donor
star, but the nature of the variability is still uncertain. I will discuss the work I
have lead on dusty ULXs and highlight the importance of coordinated multi-wavelength
observations.