real-life Gus Dundee
The Gus Dundee fight episode was clearly taken from an actual incident involving Primo Carnera, who was the real-life inspiration for Toro Moreno. Ernie Schaef was a heavyweight who died after fighting Carnera, but it was generally acknowledged that the beating he took from his previous fight with Max Baer had done all the serious damage. Baer, of course, plays Buddy Brannen here, so he's essentially playing himself in re-creating the incident.
What makes this especially curious is that Baer, according to his son, was always torn up over having killed Schaef and another man, even putting their kids through school with his own winnings. Max baer Jr. was particularly outspoken about this after "Cinderella Man" came out, in which his father was portrayed as a bloodthirsty, homicidal fighter (pretty much like Buddy Brannen). Max Jr. was upset with Ron Howard with depicting his father this way, insisting his own feelings about what had happened were just the opposite.
Which makes me wonder why Baer took this role, when he must have realized that fight insiders would recognize the real-life parallel.