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Luigi's Mansion: Dark Moon
Mummies first appear in the Old Clockworks during the the second mission. They slowly walk towards Luigi, and once they are close enough, they try to grab him, causing 20 damage if successful. Luigi must remove their mummy wrappings, as they cannot be sucked up into the Poltergust 5000; if a Strobulb charge is used on one, it will charge a small distance directly at Luigi, and if it hits a wall, it will collapse and one of its wrappings will come loose. Luigi must use the Poltergust 5000 to suck up the loose wrapping, use a Power Surge, and the wrappings will fly off, revealing a Greenie, which is holding fake arms and legs. If Luigi is not fast enough, it will get back up. Alternatively, Luigi may also shine the Strobulb while he is behind a source of fire; if the mummy runs into the fire, its wrappings will automatically burn off, revealing the Greenie. After this, the Greenie will act normally.
Luigi's Mansion 3
Mummies return in Luigi's Mansion 3, where they appear inside the pyramid in the Tomb Suites. They have the same behavior as they do in the previous game. Here, mummies can have either Goobs or Slinkers inside of them, or in one case, a Golden Goob. They also appear in the Master Suite.