Two new lost screamers

Yeah, all those fake logos were common at the time, however I'm pretty sure about the one that was on that video's thumbnail. The content of the screamer we both remember is the same, and it was an unusual jumpscare, so I'm sure we are referring to the same video, so it is possible you're memory is playing tricks on you about the thumbnail.

I guess we'll only find out when and if we manage to recover it from the Wayback Machine...

Yeah you're probably right about the thumbnail since it's been like 10 years and I do feel like I've seen that picture you posted before.
But to sum up: the video had a fanmade thumbnail of the game (likely the one you posted), the title was something along the lines of "Super Smash Bros 4 - Leaked Trailer" or something like that, had the Brawl trailer involved in it somehow, was about 2-3 minutes long, was on Youtube in 2011-2013 (I remember watching it in 2012 iirc) and the screamer was The Exorcist girl (the same one used in the Scary Maze Game) and the screamer happened early on in the video. 

I've tried to put a bunch of old Super Smash Bros 4/Universe video URLs into the Wayback Machine to see if any of them are archived and if the video is in the recommended section but none of them are archived sadly.

*your

Sorry for the late response, I'm unfortunately pretty busy nowadays.

Anyway, yeah, your summary is spot on. I can also add the fact that the screamer was very early on (like some seconds in) and that the audio during that black-screen introduction before the jumpscare was the exact same as the "Super Smash Bros Brawl" trailer (the sounds of Mario, Link, Kirby and Pikachu gathering together in their "Melee" appearances); I'm 100% sure about these details.

Anyway, did you have some luck with the Wayback Machine since you have written the last post? I didn't so far...

WOW I was not able to login for a while and now that I'm back you were able to find the first screamer, amazing 
It's even more amazing that there was somebody else (Toonandy) here that remembered that screamer (as well as the Sommo Luminescente 24k missing card from my other thread). 

Now, going back to the video, the one found by RandyMediaTime is probably it, but there are still a couple of doubts in my mind.

Let's go through the pros first, almost everything I remembered about the video is in there exactly how I remembered them, from the BatBoy-like screamer at the end (an image I've only ever seen inside that video by the way, and that is much less scaries than I remembered ahah), to the illusions inside the video (which I vividly remembered), to its lenght, to the Movie Maker style and so on.

The are a couple of cons however, starting from a different thumbnail from the one Toonandy and I remembered (which could be explained by a direct change by the author or by Youtube evolution that messed with the thumbnails of old videos) and the fact that I remembered that the video kept telling the watcher to wait for the final illusion and to watch it closely.
About the last con however I may be misremembering this fact for a couple of reasons, the first one being that this video was shown to me from a person that wanted to scare me, so maybe it wasn't the video that told me to wait for the last illusion, but maybe it was this person and I got the two things mixed up; the second one being that at the end there really was an illusion that needed to be seen closely, so maybe I misunderstood that.

All in all, I can say with 95% certainty that this is it, and I'm glad it is still up and running on Youtube, differently from "SM64 Big Star Secret", as this video is now somehow a charming memory of mine.

Now we only need to find the other screamer I was looking for, so let's try something similar to what we tried with "Illusioni Ottiche" shall we?