Ghosts were the spirits in Raiders of the Lost Ark which appeared after the opening of the Ark of the Covenant. Soon after the opening, they caused the deaths of the Nazis who were there and they also made Colonel Dietrich's head shrink, Toht's face melt, and Rene Belloq's head explode.
In Lego Indiana Jones
Ghosts appear in the level "Opening the Ark" in the cutscene where Belloq and the Germans open the Ark. In this version, they look like stereotypical white Lego ghosts. Ghost have no name. Although this is not true, it really is not true.