"Humbug" was the twentieth episode of the second season of The X-Files science-fiction television series created by Chris Carter. It was also designed to be the very first comedy episode in the series, and employs black humour throughout the episode.
Mulder and Scully must find the paranormal among the abnormal when they are sent to investigate a long standing series of ritualistic killings which match no known patterns, the latest of which is the death of the "Alligator Man," just one of many sideshow acts around which the town of Gibsonton, Florida is built.
Mulder's supernatural focus for the episode is the Fiji Mermaid, a sideshow attraction that first appeared in the mid-1800s. During their investigation, Mulder and Scully shift their suspicion around three of the inhabitants of the city, "The Conundrum", a geek who never talks and will "eat anything", "Dr. Blockhead", a "body manipulator" (a "block head" who can drive nails up his nose, as well as a master escape artist), and "Jim Jim, the Dogface Boy", the local Sheriff.
During their investigation, Scully points out to Mulder that the both of them have been wrongly suspicious of many of the "circus freaks" in town simply because of their abnormalities, which could be considered racial profiling of a sort.
This creature ends up being Leonard, the underdeveloped fetus in fetu twin of Lanny, played by Vincent Schiavelli, a resident of Gibsonton. Leonard is actually capable of exiting and then returning into Lanny's body. Lanny mournfully suggests that the motivation behind his brother's attacks is that he is seeking a new brother, by attempting to burrow into their side. Lanny later dies from an unrelated drinking problem which severely damaged his liver, and Scully says that his autopsy revealed many differences in the arrangement of his blood system, esophagus, etc. which were almost umbilical in nature.
At the climax of the story, Mulder and Scully observe "The Conundrum" lying on the ground while chasing Leonard. It is strongly suggested that "The Conundrum" was attacked by Leonard, and ironically ended up eating him. At the end of the episode, Mulder observes "The Conundrum" in a state of discomfort, and he replies "Probably something I ate." Thereby uttering his first line in the show, and leaving confused looks on Mulder and Scully's faces.
The episode ends with Dr. Blockhead philosophically commenting to Scully about how what the future really has to worry about isn't abnormal circus freaks like the inhabitants of Gibsonton, but instead everyone turning into people that look like Mulder: buttoned-down suit-and-tie wearing office drones with no individuality.