From the Super Mario Wiki
Doppels are ghost-like creatures found in Smithy's Factory during the events of Super Mario RPG: Legend of the Seven Stars. Doppel likely gets its name from the term doppelgänger, an English loanword from German that means a ghostly double.
In battle, these enemies fight alongside Lil' Boos, Glum Reapers and Puppoxes. Unlike most ghosts, Doppels have an average physical defense and magical defense. Doppels are very fast and attack with a variety of ghost-type moves. It is unknown what connection this ghost has with the Smithy Gang. They are related to Shadows, another species of enemies found in Kero Sewers.
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