This image, as well as the two acompanying videos, were posted to 4chan's /v/ board on the 4th of November. The image and video details what appears to be two unreleased Mii Fighter costumes, more specifically Mii Fighter hats of Mallow from Super Mario RPG as well as a Cacodemon from DOOM. Nobody knows who posted these videos and the image, as nobody has come forward as of the writing of this post.
-= Points =-
+ As most Smash Ultimate modders would attest, it is a somewhat difficult task to not only make such high quality costumes, but to also get them to run in-game without breaking or looking off. According to twitter user @Miguel92398 in this tweet chain:
"But the hard part was not the model but rather the texture. I can't compress the texture due to it being over the compression size. So I posterize it to make it lower."
+ In spite of many claims to the contrary, nobody thus far has been capable of accurately replicating what is shown in these videos. There have been attempts to recreate the Cacodemon Hat from the video, but none have been able to accurately recreate the hat in the image and videos.
Left: CacoMallow post
Middle: Recreation A, done in blender
Right: Recreation B, in-engine mod
~ The hats are very detailed and high quality. While it's entirely possible that this is an indication of them being real, it's also possible, though less likely, that dedicated enough fans could accurately replicate this, considering the trouble that @Miguel92398 had trying to get his Mallow Hat mod looking right.
~ The timer in the top-right corner is stopped at 2 minutes and 30 seconds. This is consistent with a prior image leak of Ken from Street Fighter, who is coincidentally also in the image and video, in the same pose no less. While they are similar, it's also possible, assuming this is fake, that this was done deliberately by the faker in order to make the images and hats seem more legitimate.
~ Sabi has contacted one of her sources to ask about the hats, and while they believe them to most likely be faked, they could not definitively prove or disprove their legitimacy at this time.