UPDATE: Aaaaaaand those videos are now gone. Sorry, folks!
If you're adverse to spoilers, you might want to stop reading now.
While I don't normally report on leaks or rumors, it's hard to argue with these videos, which appear to reveal fighters like Bowser Jr. and Dark Pit in the 3DS version of the upcoming Super Smash Bros.
The person playing in these videos is listed as "ESRB0083," which would suggest the copy being played is an early version submitted to the Entertainment Software Ratings Board. One way or the other, it wouldn't be a surprise if these videos magically disappeared later today.
Also, why is it that leakers always have such horrible ways of capturing video?
In the meantime, watch away.