Warning - This article contains potential spoilers for The Falcon and the Winter Soldier.
The identity of Erin Kellyman's character in The Falcon and the Winter Soldier has been a big mystery ever since she was cast. The leading theory thus far for her true identity has been Melissa Gold, a.k.a. Songbird. She was originally a member of the all-female villain group The Grapplers, who were likely shown fighting John Walker.
Songbird is also one of the original members of The Thunderbolts in the comics, a team of villains acting as heroes, which has also been rumored to appear in this series. Even Batroc the Leaper, played by Georges St-Pierre, is returning, likely joining the team.
Another reason why Songbird has been such a strong candidate is the power Kellyman seemed to exhibit in one scene on set. An eyewitness reported that Kellyman's character seemed to have the ability to control people, who were described as being in a “trance.” One of Gold's original powers in the comics was the ability to mind-control people with the sound of her voice.
Eventually, through merchandise and trailers, it was shown that Kellyman's character was actually a member of the Flag-Smashers. However, a new description for The Falcon and the Winter Soldier merchandise has been added, revealing who exactly Erin Kellyman will be playing. Yet, it's a character not many had assumed.
ANOTHER GENDERBENT VILLAIN
On Zazzle, in the “About This Design” section, a description for a promotional t-shirt The Falcon and the Winter Soldier now specifies Erin Kellyman's character as Karli Morgenthau:
“Check out this paint splatter graphic featuring Karli Morgenthau, leader of The Flag Smashers!”
WHO IS KARL(I) MORGENTHAU?
In the comics, Karl Morgenthau, also known as Flag-Smasher, was the leader of U.L.T.I.M.A.T.U.M., an anarchistic group bent on destroying the concept of nationalism to bring about a united world. If the description for this merchandise is correct, Karli is also presently the leader of this group, now called The Flag Smashers.
It's doubtful that this is Karl's daughter or relative, as her name seems to be a feminized version of his own. This means that Marvel Studios has once again changed the gender of a character, similar to Annette Bening's Mar-Vell in Captain Marvel and Hannah John-Kamen's Ghost in Ant-Man and the Wasp.
The only wrinkle is that in the comics, Karl Morgenthau doesn't have any superpowers, whereas Kellyman seemed to exhibit some in one scene. The witness even pointed out that she didn't seem to be using any device either. However, it could easily be revealed that it was simply too small for this person to distinguish one on set from such a distance, or that Morgenthau will indeed have superpowers.
It will be interesting to see what other changes Marvel Studios has made to the character to modernize them for audiences.