Gender Bender

Investigating a man who died of an overdose of pheromones, Mulder and Scully are led to a simple living community sect called the Kindred and a killer who can change between male and female forms.

Tropes:

• Ambiguously Related: The manner in which the alien shapeshifts between genders, as well as their Super-Strength, is very similar to the Alien Bounty Hunters introduced in Season 2. It's unclear if there is any connection between the two groups of aliens (the Kindred display the ability to teleport, something the Bounty Hunters never do).
• Crop Circles: After the aliens leave at the end of the episode, Mulder and Scully come across a large crop circle in the field. It's implied it's a print of their spaceship.
• Date Rape Averted: One of the aliens manages to almost seduce Scully before Mulder bursts in and throws him off her.
• Gender Bender: The episode's title is self-explanatory. The aliens can switch sexes at will.
• Human Aliens: The monsters of the week look exactly like humans.
• Humanshifting: The Monster of the Week shapeshifts from male to female and back, though s/he only seems to have a single appearance for each gender.
• Living Aphrodisiac: The aliens themselves.
• Mars Needs Women: A variation in that the killer is implied to be a Rogue Agent acting against the mores of their community.
• Monster of the Week: Even though the episode featured aliens (apparently), this was one of the few times where they made an appearance and they were not a part of the mythology.
• Mystery Cult: The Kindred.
• No Communities Were Harmed: The Kindred have many similiarities to the real-world Shaker sect (formally the United Society of Believers), including frugal communal living and modest dress, manufacture and sale of high-quality household goods, strict celebacy (the main reason the Shakers have shrunk from a peak of 6000 members to 3 as of 2023), incorporation of highly-choreographed ritualistic dancing in their worship, and a dualistic view of God and sex (Shakers believe God is both male and female, and that there is both a male and female Christ (Jesus and their founder Mother Ann, respectively)). There are also some elements of Amish thrown in, such as objections to having their photographs taken and a rejection of technology (contrary to popular belief, the Shakers never shunned technology).
• Ninja Pirate Zombie Robot: There's so much going on with the Monsters of the Week that it gets a bit overwhelming. They're human-looking aliens who have no resemblance to any other aliens in the show, who switch genders after they have sex, and also kill their sex partners. And they're not very good-looking, but their touch can seduce. And there's something going on with the clay they use. Oh, and they're immortal. And as if all that wasn't enough, they have a No Communities Were Harmed Shaker or Amish schtick going on as well.
• OOC Is Serious Business: Scully nearly ends up sleeping with Brother Andrew before Mulder interrupts. She throws up afterwards, implying she'd absorbed enough toxins from bodily contact to make her own body reject them.
• Out with a Bang: Sleeping with the aliens is almost inevitably fatal to the human.
• Pheromones: The plot is kicked off by a man who suffered an overdose. As it turns out, the Monster of the Week uses these to seduce its victims.
• Sex Is Evil, and I Am Horny: Seems to be going on with Brother Andrew, who's very drawn to Scully despite the dictates of his community.
• Sex Shifter: The Monster of the Week is a member of an (apparently) alien humanoid species whose biological sex changes every time after they have sex.
• Space Episode: It is heavily implied the cellar door leading to the cave underneath the barn is a portal to the aliens' home planet, which Mulder unknowingly stumbles into without realizing the implications. This explains the strange glowing organic-looking mesh that Mulder touches with his fingers. Mulder has an Oh, Crap! moment when he realizes this after the doorway is mysteriously filled with concrete at the end of the episode.
• Stepford Suburbia: Except with a simple living community similar to Shakers or Amish.
• Stock Footage: The dance music heard in the nightclub is actually reused soundtrack written by Mark Snow for the film In the Line of Duty: Street War.