What nickname does Fox Mulder earn because of his paranormal beliefs?

Fox Mulder earns the nickname “Spooky Mulder” because of his paranormal beliefs.

The nickname reflects Mulder’s reputation inside the FBI as an investigator fascinated by unexplained phenomena, extraterrestrial life, psychic abilities, and government conspiracies. His interest is not merely professional: the reported abduction of his sister Samantha when he was twelve drives much of his search for hidden truths.

Mulder’s beliefs lead him to the FBI’s X-files, a collection of unsolved cases involving strange or potentially supernatural events. Dana Scully is assigned to work with him partly because her scientific training makes her a skeptical counterweight to his theories.

A common mix-up is treating “Spooky Mulder” as his formal FBI title. It is an informal label describing his colleagues’ view of him. Mulder’s full name is Fox William Mulder, and he is played by David Duchovny. The nickname appears in the series’ central premise and becomes one of the character’s defining identifiers.