The X-Files Episode The Host Aired 32 Years Ago
Generally speaking, there are two different kinds of episodes of The X-Files. There are the serialized mythology episodes, which deal with the central, ongoing story about aliens and the government conspiracy surrounding them. These kinds of stories usually get top billing each season as the premiere and finale with a few more sprinkled in throughout the season. Then there are the procedural Monster of the Week episodes, during which Agents Mulder (David Duchovny) and Scully (Gillian Anderson) investigate standalone cases entirely unrelated to aliens. While mythology episodes would sometimes take on an outsized importance in the eyes of fans, the vast majority of The X-Files were Monster of the Week stories.
The term monster is used loosely here, because it could refer to any weird new creature, case, or even superpowered person. Regardless, there were a lot of different monsters on the show, but all of them fall short of one introduced during a season 2 episode called The Host.
The Host

The Host was the second episode of season 2. It takes place during a period when the X-Files division of the FBI has been shut down. Mulder is sent on a case involving a waterlogged body found in the Newark, New Jersey sewer system, and he is convinced it is a punishment from his bosses at the FBI. Over the course of the investigation, however, he finds out that this is indeed an X-File.
When Agent Scully performs an autopsy on the body, she finds a flukeworm in its liver. Soon after, a city sanitation worker is attacked in the sewer system by what he believes to be a python, but the giant bite mark on his back matches the mouth of a flukeworm, although much larger. After the sanitation worker dies, Mulder visits the sewage treatment plant, which has accidentally captured a creature that has the size and shape of a man, but with the face and mouth of a flukeworm. Soon after, the Flukeman, as the creature comes to be known, begins attacking workers at the sanitation plant in an effort to escape.

There are a number of reasons why the Flukeman is so highly regarded by fans. For one thing, his look is original. While there are man-like and sea creature elements that harken back to the classic Creature from the Black Lagoon, the bright white monster and his giant oval flukeworm mouth made him instantly memorable. The episode was also executed with cinema-level practical creature effects, which were rare on television at that time. The Host was a tightly written sci-fi thriller story by X-Files creator Chris Carter. It also contained a timely real-world element, as the Flukeman is suggested to be a product of the Chernobyl nuclear disaster in Ukraine, which occurred less than a decade before this episode ran. The episode aired during a time when the show was exploding in popularity, and since it was not part of the show mythology, it was an easy episode to revisit without having to watch a bunch of other episodes to get caught up first.
Since then, the Flukeman has become an unofficial X-Files mascot for Monster of the Week episodes overall. Outside of aliens, the monster you are most likely to find on X-Files merchandise is the Flukeman, which is surprising since he is only in one episode of the show. For example, when Lego released their official X-Files set earlier this year, it included a bunch of human characters, an alien, and just one other creature: the Flukeman.
Lots of interesting monsters came and went throughout the series, from the liver-eating Eugene Victor Tooms to the terrifying inbred Peacock family, but none stuck in the minds of fans quite like the Flukeman.
Source: Polygon
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