At one point in development, there were plans for an NES release that ultimately never came out.
In Birdie's stage there is graffiti of the former Capcom USA VP of Sales and Marketing, Bill Cravens.
There's unused audio in the game files for a "Fire Kick", along with unused graphics that suggest Ryu and Ken were planned to have a fourth special move.
Capcom released a "Deluxe Version" of the game's original arcade cabinet which featured pressure sensitive pads. Players would have to punch the pads in order to execute attacks, and the game measured the pressure applied to result in light, medium or heavy attacks. These machines were often subject to heavy wear and tear due to the nature of hitting the machine.