Mario Slug is a Metal Slug fan game created by Gabe Harbinson. It is still in development, and at least three levels are in completion. It consists of Mario saving the Mushroom Kingdom by Bowser's forces, now strengthened by the possession of Ptolemaic and Rebel vehicles. Mario also has to save Toad's as POWs in advance. Two-player mode is also supported, which means that the second player can play as Luigi. The SV-001 can be used as well.
Super Grenade (uses Bullet Bills as projectiles)
Koopas (The spiritual version of the rebels, can throw grenades and use rifles)
Sword-wielding Goomba-like enemies.
A.P.C (Unlike the original version, this one develops koopas and gombas)
A big Bowser robot on two Emain Macha tracks piloting by Kamek.
Bura Gariae (Edited version with the Bowser's army logo instead of the Amadeus syndicate and throwing bombs like the Hi-do ones)
Claw Unit (Controlled by Captain Syrup in a Ptolemaic Saucer, a Wario land character and antagonist from same game)