Just saw this, what is it?

[3D Player 2004]

I'm confused on what this thing is.

 

[Koopakoolklub]

A tournament in Smash, perhaps?

Adventure Mode?

I haven't a clue, either.

 

[MoonAge]

It's Classic Mode, probably.

 

[Mario4Ever]

Most likely, except it incorporates a branching path system instead of everyone having to fight the same sequence of characters.

 

[SonicMario]

I think it's a branching path Classic Mode. I think right after that part of the 3DS we even had Master Hand show up not too long after. If it is that, that sounds really cool.

 

[3D Player 2004]

In case anyone wants to know, this clip is from this video.