Playing as the Mummy causes the setting to turn into Halloween. The Trees are bare, the Rivers are orange, the boulders are replaced by pumpkins, and the grass turns orange. The Mummy moves its legs during the run, giving it an illusion of running. The Mummy makes typical “mummy” noises such as strangled breathing and “raargh”.
The "raargh" noises that Mummy may emit come from the Zombies from Terraria.
Mummies started to capture the popular imagination when Egypt was colonised by Great Britain in the 19th Century and they were viewed as romantic figures. This changed with the release of the Boris Karloff film, The Mummy, in 1932 when a mummy was portrayed as a monster / horror figure.