Changelings are one of the races in the world of Equestria. Canonically, they are bug-like creatures who can take on the appearance of other ponies, which deception they use as a way of feeding off of their victims' love. A changeling swarm led by Queen Chrysalis impersonated Princess Cadance and invaded Canterlot during the events of "A Canterlot Wedding". They have no further appearances in the show until season 5, where one appears as a wedding guest.
Differences from CanonEdit
In the alternate universe of Austraeoh, Changelings have mostly the same appearance and abilities. They can feed on any emotion in general, rather than exclusively love. They have the ability, given enough time, to steal memories and personalities, allowing them to almost perfectly impersonate another. They also have the ability to merge together to create larger forms, such as walls or giant creatures (at one point, Chrysalis uses them to create an animated avatar of herself). They are led by Chysalis on the light side of the world, and by Tchern on the dark side. The reason given in the story for why the invasion of Canterlot did not take place in the Austraeoh universe is because the chaos rift made Equestria a less appealing target. Hence, Chrysalis stayed in Val Roa to build her power there.
Changeling tactics generally involve instilling fear and anger into others, which emotions they can draw upon to become even stronger. Dopplegangers cleverly placed in pony society are used to sow discord and distrust among groups, as well as for gathering information.
Interestingly, there seems to be distinct variety of changeling which takes on the form and memories of another pony, but has no awareness that they are actually changelings. Notable characters in this group are Elma Boreal and Ebon Mane. It is likely that these drones are placed throughout the world to serve unwittingly as information probes, providing eyes and ears for Chrysalis. This would explain how Chrysalis knows intimate details about many characters, including Rainbow's relationship with Applejack. Celestia reports that many drones of this sort were discovered in Equestria when Rainbow broke their empathic link in Stratopolis.
"The two sisters, Chrysalis and Tchern, were driven to the far corners of Equestria. They took with them scores upon scores of ponies—minions who tragically shared in the curse that the crystals had brought upon them. They could no longer harbor emotions like the naturally born ponies of this plane. Instead, they had to mimic others in order to feed off of feelings of love, passion, and distress. The sisters became queens of a nomadic brood, and they telepathically lorded over the mutated ponies who pledged their undying allegiance to them. The only way the mortals could now survive was by operating under a hive mind with Chyrsalis and Tchern at the center. The last time we ever saw them, they had fled to the dark side of the world, where undoubtedly they had constructed a kingdom of malevolence where no sunlight or moonlight can be glimpsed... to remind them of the true love that they have forsaken." (Urohringr, "That Which We Drive Away")
While changelings are in their natural forms, they cannot be sensed by chaos beasts.