Super Mario Bros. Crossover

Super Mario Bros. Crossover is a fan-made remake of Super Mario Bros., Super Mario Bros. Special, and Super Mario Bros. 2 (what became The Lost Levels elsewhere) where you can play as different NES characters using their respective powerups: Mario, Luigi, Link, Samus, Simon Belmont, Mega Man, Bass, Bill Rizer, Ryu Hayabusa, and Sophia III.

Mario and Luigi
Present in Mario and Luigi's Super Mario Bros. 3 skins are quite a few unused sprites. While most of them seem to be intended for skin differences (introduced in Version 2.1), they also seem to be leftovers from the sprite-ripping process.



Sprites of Mario holding out his arms. Used for a running jump in Super Mario Bros. 3.



These sprites were used in previous versions when Mario climbs vines and when going down a Goal Pole. Sprites of Mario's back turned are used instead.



Sprites of Mario intended to be used for carrying an enemy's shell and then kicking said shell. This can't be done in the final version.



Because there are no slopes in the game, this goes unused.



Mario doing backflips. This would be used when Mario jumps while under the effects of a Starman.



The Super Mushroom, Fire Flower, and Starman on Mario's sheet are unused; the used ones are on the map skin.

Link


Even though Link can't swim, he has swimming sprites in his sheets, reminiscent of his swimming sprites in the platforming sections of Link's Awakening.



The Magical Shield. It was probably removed due to the fact that not that many enemies throw projectiles other than Bowser.



A HUD graphic for the shield.



The Stepladder from The Legend of Zelda. This would let Link walk across small gaps. He can easily jump the over the gaps here, which is probably why it was removed.

Samus


The Long Beam is part of the Mushroom upgrade, Samus begins with the Morph Ball and Bombs, and the Missiles are collected from enemies. As such, the Missile Pack, Missile Extension, and High Jump Boots are unused.

Simon


These sliding sprites are unused. Like with Mario's SMB3 sprites, they go unused since there aren't any slopes.



The Rosary and Invisibility Potion can be found in Simon's skins. In Castlevania, the Rosary kills all onscreen enemies, while the Invisibility Potion gives Simon invulnerability for a few seconds. Rather than being two of Simon's powerups, they appear in the Castlevania overworld skin as the Lucky Star and Starman respectively.

Mega Man


Mega Man has unused swimming sprites that depict him riding in the Rush Marine from Mega Man 3



The Rush Jet adapter from Mega Man 3 is also present. Supposedly, this would've been added to help players deal with Lakitu more easily.

Bass


Sprites for Treble Boost and Bass in his Treble Adapter from Mega Man 10 are present in Bass' sheet.



Bass' Dr. Wily sheet doesn't have the sprites for Treble beaming down and standing, but has sprites for the Wily Capsule from Mega Man 4 over the Adapter. It's probably a placeholder. It may sound like a letdown, but at least we don't get that annoying beep!



As for the Mr. X skin, uuuuuh...

Bill


The "Mass Destruction Falcon" from Contra is present in Bill's skins, and would have let Bill destroy all enemies on-screen. A powerup called the "Lucky Star" was introduced in v3.0, which does the same thing.

Ryu


The "Splitting Your Body" item from Ninja Gaiden 2. This powerup would create an orange clone of Ryu, who would attack at the same time as Ryu. Possibly removed because of difficulty programming it. Despite the power-up being unused, the Ryu clone is a skin for Ryu.

Sophia III


These sprites suggest that Jason was going to be able to get out of the Sophia III and walk around, but he's unable to do so in the final version and the only time we see him out of the thing is when he's selected on the character roster.



Sprites for the Thunder Break weapon from Blaster Master. This powerup, when used, would spawn a lightning bolt from below the Sophia III, passing through objects and destroying enemies it touches.

Final Fantasy


Fighter, Thief, Black Mage, and White Mage sprites from Final Fantasy (as well as upgraded forms, mostly from Final Fantasy III) can be found in one sheet through a Flash decompiler.

Gradius


An unused sheet of the Vic Viper from Gradius can be found the same way. According to Pavlina, the screen would have autoscrolled. It may have been removed due to clashing with the overall style of the game, and also because you could break the game completely by flying to the top of the screen and spamming shots to take down Lakitus.

Map


Sprites for disintegrating blocks.



While v3.1 introduced the Lost Levels, these are based on its appearance in Super Mario Bros. Deluxe where the wind mechanic wasn't implemented, so the leaves go unused.

Super Mario All-Stars


These yellow flag sprites are present in the skin for Super Mario All-Stars. In that game, these flags appeared on the sides of the castles in x-3 levels.

Super Mario Bros. Deluxe
Present in the overworld sheet.



A Yoshi egg from Challenge Mode, probably related to a similar feature.



Red Coin sprites from Challenge Mode, probably related to a similar feature.

Interface


Skull, Red Coin, score, and Yoshi egg icons.