A "BONUS COIN" graphic. It's a more plain version than the one seen in the arcade version during the first stage intermission, but since this port doesn't have the intermissions, it goes unused.
Interestingly, this graphic was removed in the "Classic Serie" version.
A larger, more arcade-accurate fireball. Most of the first sprite was overwritten by other graphics.
These are similar to the sprites used in the "Classic Serie" version, but not identical.
A Shellcreeper in its shell. It seems like Shellcreepers originally would have went into their shells after being flipped over like in the arcade version.
Part of an early sprite of a Shellcreeper that's been flipped over. This occasionally appears for a single frame when a Shellcreeper falls into the water due to a graphical glitch, but is otherwise unused.
Notably, this sprite heavily resembles a sprite seen in the game's manual.
A duplicate of one of Mario's walking sprites. The bottom-right tile was overwritten by other graphics.
Icicles, which don't appear in this version. The palette used for Freezies doesn't fit them very well, suggesting that it was changed at some point.
These sprites would later be used in the "Classic Serie" version, albeit in a slightly modified form.
A duplicate of the graphics used when a Freezie freezes a platform. These are background tiles instead of being sprite tiles like the used versions are, which explains why they aren't used.
A duplicate of one of the sprites used when hitting a platform. Similarly to the above graphics, this is in the wrong graphics bank; in this case, the sprite bank.
Frozen letters? Who knows what these would have been used for. Interestingly, these letters are arranged in the same way as their normal counterparts in the ROM, suggesting that there were other letters that got overwritten at some point.
A bulge in one of the pipes. It seems like these originally would have appeared while enemies were coming out of the pipes like in the arcade version. None of the sprite palettes match the pipes, which may be why this wasn't used.
Unused tiles for the pipes. While some of these tiles are duplicates of used ones (and each other), the others seem to be for an earlier version of the pipes.
Mario Bros. Classic Serie
In 1993, an enhanced version was released in Germany and Italy under the label "Classic Serie". In addition to retaining graphical and gameplay improvements from Kaettekita Mario Bros., it restores the missing stage intermissions and adjusts the music and gameplay speed to match the 50Hz PAL refresh rate.