Mummy Generators are usually found inside Egyptian-like locations. It resembles a phone booth with a "MUMMY" sign on top. Mummy Generators will endlessly spawn Mummies until it's destroyed. Some generators spawn Dog Mummies.
The Mummy Generator appears in Metal Slug Defense purchasable for 120 medals. A few generators are found in a few levels as obstacles.
A variant that spawn Mummy Cats appears in Metal Slug Attack as a Rare Boss unit for the "Pharaoh Rebirth" Extra Ops. Unit parts can be earned by playing through the second level of the Another Story "Arabian Romance".