Goldcap, Decepticolt and Zappityhoof, better known as the "Pseudocorns", are an evil team of unicorns and the main antagonists of My Little Pony: Friends Forever issue #25.
Under the belief that Twilight Sparkle used similar methods, Goldcap, Decepticolt, and Zappityhoof decided to create a forbidden magic potion to turn themselves into Alicorns and become famous. In order to perform the spell, the Pseudocorns stole Rainbow Dash's wings while she was sleeping to use in their potion, getting Twilight and Rainbow Dash to try and stop them.
At the beginning of the comic, Rainbow Dash wakes up one morning to find that her wings have been completely removed, causing her to panic. She immediately goes to Twilight's castle in order to find out what happened to her wings.
Using a Tramalocation spell, Twilight locates Rainbow's wings and is shocked to find that three unicorns removed Rainbow's wings with magic.
While secretly being observed by Twilight and Rainbow, the three culprits boast about their success and express their desire to become Alicorns and become famous, believing that they would automatically become members of Canterlot society, with Zappityhoof in particular desiring to become an Alicorn princess. While still being observed, the three unicorns fully explain their entire plan; after soaking the wings in the noon-time sun, they would make the wings absorb the twilight glow of the moon, draining their essence to make the potion, which they would then drink in order to become Alicorns.
Horrified with their intentions, Rainbow and Twilight set out to stop them and retrieve Rainbow's wings after Twilight nicknames the group Pseudocorns, since they wouldn't be true Alicorns if they used their potion. Instead of waiting to formulate a plan or strategy, Rainbow forces Twilight to simply go and stop them, planning to simply sneak up on them and take them by surprise.
Using a camouflage spell to hide them and a teleportation spell to take them to the Pseudocorn's location, Twilight and Rainbow try to sneak up on the Pseudocorns and get Rainbow's wings back. Twilight flies above the Pseudocorns and tries to sneak up on them, however, since she can't camouflage her shadow, she is spotted by the Pseudocorns and imprisoned inside a magical net. When Rainbow tries to free Twilight from her prison, she is easily beaten and detained in another net due to forgetting that she can't fly away.
With Rainbow and Twilight imprisoned, the Pseudocorns finally manage to drain Rainbow's wings of their essence and contain it inside a small bottle. When Twilight angrily tells Goldcap about how forbidden their actions are, Goldcap defensively claims that Twilight just wants to hog the power and freedom of becoming an Alicorn to herself. Zappityhoof asks Twilight if they are any different from Twilight when she was a unicorn, and Twilight states that her wings weren't stolen from somebody else, which all three Pseudocorns don't believe.
With enough time and nothing to lose, Rainbow comes up with a plan to defeat the Pseudocorns by having Twilight use a spell to transfer her consciousness into Twilight so she can use her magic while Rainbow flies Twilight's wings. Using a spell to pair their minds, Rainbow Dash and Twilight use Rainbow's superior flying abilities and Twilight's superior magic to easily beat the Pseudocorns into submission and defeat them using a "genuine pseudo-Sonic Rainboom".
After defeating the Pseudocorns and getting the potion containing the essence of Rainbow's wings back, Twilight tells the Pseudocorns that she earned her wings by studying, learning and making friends, and punishes them for misusing magic by removing it until it naturally comes back to them. Twilight and Rainbow then leave the Pseudocorns in the forest where they found them.
Friendship is Magic