  We propose that the intermediate luminosity optical transient NGC 300
OT2008-1 was powered by a mass transfer episode from an extreme Asymptotic
Giant Branch star to a Main Sequence companion. We find a remarkable similarity
of the shapes of the light curves of the several months long NGC 300 OT2008-1
outburst, of the three months long 2002 enigmatic outburst of the B star V838
Mon, and the twenty-years long Great Eruption of the massive binary system Eta
Carinae that occurred in the 19th century. Their similar decline properties
hint to a common energy source: a gravitational energy that is released by
accretion onto a main sequence star. These events populate a specific strip in
the total energy vs. outburst duration diagram. The strip is located between
novae and supernovae. We add recent transient events to that diagram and find
them to occupy the same strip. This suggests that some intermediate luminosity
optical transients are powered by accretion onto a compact object (not
necessarily a main sequence star). These transients are expected to produce
bipolar ejecta as a result of the geometry of the accretion process.
