<< Wasn't he the dude that was portrayed in that movie "fat boy little man" or something? >>
Well, kinda. The actual accident happened after WWII. In the movie, the incident was portrayed as happening before the first trinity test and before the end of the war. Also, the chractor played by John Cusack (Michael Merriman) was fictional in nature and used as a narrative.
BTW, if anyone thinks Fat Man and Little Boy is an objective documetary, they've been hoodwinked.