Fun Fact: The referee in Punch-Out!!! looked a heck of a lot like Mario.
Nintendo wanted to port its Punch-Out!!! arcade game to the NES, but they had a problem: there was no way the NES could replicate the full-size, wire-frame boxer from the arcade properly. So instead, they created the tiny character of Little Mac, such that players could clearly see their opponent during a fight.
This also helped with the creation of a story for the game. Little Mac was a scrappy boxer trying to work his way through the circuit to get a shot at Mike Tyson and the championship belt. The version of this game with Mike Tyson is the most famous, but when the licensing deal ran out, this game was sold as plain-old Punch-Out!!!, and Tyson was replaced by a character called The Dream King.
Punch-Out!!! was about timing and pattern recognition. Players had to learn when their opponents would be about to throw a punch, and what the pattern of those punches would be, and then get out of the way or block accordingly until they could counter-punch. The better the player did with their counter-punching, the greater the chance they would earn a Star, which could be spent on a powerful uppercut.
All the opponents in the game had a ton of character, but there was something special about making it to Mike Tyson at the end of the original release. Mike Tyson's Punch-Out!!! was released during the height of Tyson's career, when he seemed like an unstoppable machine. Imagine, then, being a ten-year-old kid who could look in the mirror and say “I just beat up Mike Tyson.”