In a prerelease version of Mario Stadium, there is a house visible behind the wall in center field. Further beta elements include the "Nice" pitch indication being different, and the Star gauge's design was changed.
A Dictionary mode (which lets the player look up baseball terms) is present in the Japanese version of the game. This feature was removed in the Western version of the game.
On the game's stadium select screen, one of the preview images of Mario Stadium is actually taken from a pre-release screenshot from IGN, which is evident due to the IGN watermark being shown in the bottom right corner of the preview image.