  We have confirmed that the precursor star of the unusual Supernova 1954J
(also known as Variable 12) in NGC 2403 survived what appears to have been a
super-outburst, similar to the 1843 Great Eruption of eta Carinae in the
Galaxy. The apparent survivor has changed little in brightness and color over
the last eight years, and a Keck spectrum reveals characteristics broadly
similar to those of eta Car. This is further suggested by our identification of
the actual outburst-surviving star in high-resolution images obtained with the
Advanced Camera for Surveys on the Hubble Space Telescope. We reveal this
``supernova impostor'' as a highly luminous (M_V^0 ~ -8.0 mag), very massive
(M_initial >~ 25 Msun) eruptive star, now surrounded by a dusty (A_V ~ 4 mag)
nebula, similar to eta Car's famous Homunculus.
