When minecrafters discovered sulphur or gunpowder in the nether they tested it and eventually found out "TNT" They then used it for good mining purposes. One day these miners were in a mine blowing up some tnt but on the other side was a slime that slime was jiggling around al happy when the tnt blew up it deformed it into some weird green beast with gunpowder making the skin look all light green and dark green colors. It then eventually multiplyed across the world. When people discovered it they were walking out side having fun when they saw a creepy beast creep up behind hm but the beast was so scared he frowned and blew up. We now know this beast as a Creeper