It was named #44 out of 200 of the "Greatest Games of Their Time" by EGM Issue #200 (Feb. 2006).
The "Little Mac" storyline was a product of technical issues that developers were confronted with in bringing the game to the NES. The arcade and much later, the SNES punch out games featured a see-through character to allow the player adequate view of their opponent.
This method would not work on the NES, therefore the idea of a tiny main character (Little Mac) was adopted in successful effort to provide a clear and full view of the opposing boxer.
Little Mac appears as an assist trophy in the Wii game Super Smash Bros.: Brawl.
The boxer King Hippo made a regular appearance as one of Mother Brain's henchman on the cartoon series Captain N: The Game Master.
For whatever reason, his skin was a light blue color.
In between each tournament, Little Mac jogs through New York while his trainer Doc Louis leads him on a bike. This harmless scene became one of the biggest internet sensations, at the same level of Zero Wing's All Your Base, when a SomethingAwful.com user added the caption "Nigga stole my bike!" in one of their weekly photoshop contests. The picture soon spread and became a hype, in spite of the racist undercurrent. One of the end results, a YTMND showing the animation, along with a voiced song, can be found in the related links section.
Little Mac made a return appearance as a fighter in 2005's Fight Night Round 2 from Electronic Arts.
Originally, the arcade version of Punch Out! featured a Russian character named "Vodka Drunkenski." In the NES version his name was changed to "Soda Popinski." Although it seems clear that the primary motivation for this change was Nintendo's censorship guidelines (one of which forbids liquor references), it's also possible that the name was changed at least partially motivated by a desire to tone down the character's image as a stereotypical Russian drunk.
Mike Tyson's Punch-Out!! was voted #14 in the Top 100 Games of All Time poll published by Game Informer Magazine (Issue 100, August 2001).
When the 3-year licensing deal with Mike Tyson was up, Nintendo decided not to renew it as Tyson was no longer world champion. The character was redesigned and named "Mr. Dream" and the game was re-released as "Punch-Out!". Not all passwords from the old version were compatible with the new one.