Maybe Bowser and Ganon have taken parts of their worlds to create these things. They have Bob-Ombs for heads, and they have purple auras like Ganondorf in SSBM.

 Hehe, duh.  Almost every Smash Bros platform is raised in the air hehe.

Whatever they are...they can't be that hard to fight hehe...I'll pound them back into the ground!

From that Rumor site

 Wow, i'm starting to really believe that the"cloud formations" were put in there on purpose, i get more and more convinced each time i look at it.

Except for Mewtwo...that's a stretch...

I could see Mewto returning and Lucario joining Brawl.
I agree that Mewto is a bit of a stretch.

Yeah i think that mewtwo was taking it a bit far, i see Ganondorf there instead of Mewtwo, but i'm not exactly sure. And Lucario joining Brawl would be very awesome, way better addition than Pichu that's for sure.

I think people are seeing that stuff in the clouds because they want to see it. I can see a face between "Bowser" and "Master Hand." Looking at "Bowser" a different way, it could be Birdo, with the dark clouds above forming her bow.

I can see bowser in the clouds, but the cloud on the right looks more like Master Splinter from the Ninja Turtles. My point? Clouds can look like just about whatever you want them to look like and reading into these dark spots and highlights is going a bit too far. That is a still frame from a video. Imagine the video in motion, those clouds are going to shift and change and will no longer take that exact form.

Rick however has the same theory that I posted earlier in this thread and I believe that THAT is a more accurate interpretation, but they made it cryptic so that we wouldn't know everything. They knew we wouldn't get it all so don't expect to get it all until they show it to us. They are just toying with us to see our reactions.

One thing that this speculation does bring out though, is that those clouds are almost as good at forming shapes as real clouds are which says that that is some pretty good CG.