After defeating Bowser, a key will appear with a number of coins flying outwards from it, but none of them actually fall onto the ground. This is likely a remnant of a past idea where coins would appear after Bowser's defeat, as seen in early pre-release footage. The idea was likely scrapped as the coins would serve little to no purpose after defeating Bowser, since Mario's health automatically recovers after collecting the key and returning to the hub world.