| WHAT THE HECK IS THAT?!
The naming of the page, "Eternal Feather's Duplicate", has not been confirmed by official sources.
The Duplicate is a body constructed by Franken Stein that almost perfectly resembles Eternal Feather. Both Stein and Eternal Feather have used the body to commit pranks upon Tsugumi Harudori, Meme Tatane, and Anya Hepburn.
The duplicate largely resembles Eternal Feather. In its first appearance with its head still attached to the body, it has similar height and shape as Eternal Feather's body. The face and head looks almost exactly like Eternal Feather's, except for the absence of her eyeglasses, the inclusion of a fake screw seeming to be through the head (which is subsequently removed by Franken Stein but later added back by Eternal Feather herself), and both pigtails (although at the time Eternal Feather had cut one off during her failed suicide attempt). Even the skin looks realistic enough to fool some of Eternal Feather's classmates that it is actually their friend.
The duplicate is dressed in a hospital gown and the neck wrapped in bandages, resembling how Eternal Feather appeared while recovering at Patchwork Laboratory after she sliced her neck while under Shaula Gorgon's possession.
While dressed in a hospital gown, it is not clear whether those portions of its body covered by the gown also have synthetic skin.
The steam released through the duplicate's neck bandages suggest there is some mechanism for steam operation.
The duplicate body has so far demonstrated movement only above its neck, its pigtails demonstrating considerable dexterity—enough to pick up a pen and write a person's name legibly—as well as enough strength and coordination to support the weight of the head and, acting like legs, allow the head to "run" to follow targets.
During the summer Death Bazaar in Death City, Eternal Feather attacked bystanders, having been possessed by the mind-controlling venom lacing one of Shaula Gorgon's pieces of jewelry that she sold to the NOT student. While Maka Albarn, wielding Soul Eater, struggled to contain the NOT student without hurting her, Shaula commanded Eternal Feather to kill herself, in order to hide any evidence of Shaula's presence. Eternal Feather brought her left arm, transformed into a butterfly knife, to her neck, slicing her neck as well as cutting off her right pigtail. After Maka and other tried to stop the bleeding, emergency medical assistance arrived to transport the student to Patchwork Laboratory, where an unlicensed physician held on retainer by the DWMA could perform surgery.
At Patchwork Laboratory, Franken Stein stopped the bleeding and stitched up Eternal Feather's neck injury. As per instructions from Sid Barrett, he also examined Eternal Feather's body for any evidence of mind control as DWMA Central Intelligence had noticed in other Traitors, but Stein only found a small pinprick on one of Eternal Feather's fingers.
At some point before or after Eternal Feather's injuries, Stein constructed a duplicate of the NOT student and placed it in one of the surgery beds at Patchwork Laboratory. Stein then allowed Tsugumi Harudori, Meme Tatane, and Anya Hepburn to enter the surgery room to see how Eternal Feather was recovering. Stein initially passed off the duplicate as Eternal Feather herself. The duplicate seemed to have a screw through its head, disturbing the trio until Stein showed it was a fake he had added to "Eternal Feather" as a prank on the trio. Looking at the duplicate more closely, Tsugumi also noticed its head still had both pigtails, prompting her to wonder whether Stein had not only stitched her neck but also her pigtail. Then the trio noticed the pigtail move, picking up a nearby marker to write a name onto the bed's pillow. Steam then released from bandages around the neck—and the head came off. While the trio screamed in shock, the head's pigtails managed to lift up the head and, acting like legs, allow the head to chase after the trio.
With "Eternal Feather' now revealed to be a fake, Stein picked up the head (and, in the anime, tossed it out a window) and revealed the actual Eternal Feather, who was recovering in another bed—with another fake screw through her head, which again shocked the trio.
In the anime, after Stein tosses the head out of a window, the head of Eternal Feather's duplicate scurries on away using its pigtails like legs. It is later found in the courtyard to the DWMA's girls' dormitory.
Eternal Feather procures the head of her duplicate later as part of her Halloween outfit, in which Eternal Feather wears a ring around her head to resemble an arrow going through her head while holding the duplicate's head. Upon seeing Eternal Feather's attire and her duplicate's head, Tsugumi, Meme, and Anya were terrified, perhaps because of memories of their last encounter with the head. As the head again chases the trio around a room, Tsugumi attempts to toss candy to Eternal Feather to convince her to make the head stop chasing them.