The Haunted Mansion
In the Haunted Mansion attractions of Florida, California and Tokyo the mummy sits in his sarcophagus drinking a cup of tea. An elderly spirit stands next to him, trying to understand him, but the mummy is unable to communicate with him through his bandages.
In Mystic Manor there is a possible reference to the character in the form of a dilapidated mummy Egyptian Antiquities section where it rests in a sarcophagus and then due to the curse of the Music Box it releases a swarm of insects from it's bandages
The vocal track for the Mummy singing "Grim Grinning Ghosts" was recorded by Allan Davies. It is paired with the track of the spirit next to him, who continually asks the Mummy to speak up. When the WDW Mansion was "Re-Haunted", the Mummy was one of the few characters who didn't receive a new vocal track.
An article written by the Mummy appears in an issue of the Grim Gazette, identifying him as the spirit of Amenmose, son of Thutmose I. His article criticizes both the Committee of Wandering Ghosts and the Ghost Relations Department.