Chan Ho Park and the Los Angeles Dodgers found themselves on the wrong end of MLB history on April 23, 1999, when St. Louis Cardinals third baseman Fernando Tatis slugged two grand slams in the same inning.
Before that point and in the time since, Tatis stands alone in accomplishing such a feat. Before Tatis, Mark McGwire was the only player on the Cardinals roster to ever hit two home runs in the same inning.
However, he did so as a member of the Oakland Athletics, and when the bases were not loaded for either of them.