The 7908 Locomotive was one of the many trains used by the Rebel Army to carry various supplies. The Regular Army noticed their enemy's transport lines and sent the heroes to destroy as many supplies as possible. In Metal Slug 2/X, the 7908 Locomotive serves as the third mission's midpoint in which the heroes have to jump over to another moving train. Jumping the longest gap possible nets the player 50,000 points; otherwise, they'll get 0 points for any other distance. In Metal Slug X, the players fight an R.R-Shobu that flies over this gap while Rebels continuously ambush from the right.
Sometime in Metal Slug Attack, the Regular Army got ahold of the 7908 Locomotive and repurposed it as a combat transport vehicle. Various Regular Soldiers are positioned from the locomotive's sides and attack with their weapons. In the event of an emergency, the Regular Soldiers hang on the locomotive and brace themselves while it charges forward in rapid speed. It then creates a shockwave attack by stomping on the nearest enemy before recoiling. When the 7908 Locomotive runs out of health, the Regular Soldiers tosses the vehicle onto enemy lines and run away.