Metal Slug 2 expanded the saga's universe in every direction: two new protagonists — Eri Kasamoto and Fio Germi —, new vehicles like the Camel Slug (a machine gun mounted on a camel) and the Slug Flyer, novel transformations like mummification inside the Egyptian pyramids, and a legendary plot twist: halfway through the campaign, the war against General Morden is interrupted by an alien invasion that forces sworn enemies to fight side by side. The pixel art of the former Nazca team reaches absurd levels of detail here, though ambition took its toll: the famous slowdown when the screen fills with sprites, which SNK would fix a year later with Metal Slug X. The original AES cartridge is an expensive, sought-after piece: collector fever around the Metal Slug saga has multiplied its value over the last decade.