(Some) Club Nintendo members were rewarded earlier this month with a 3DS and Wii U code to download the new Mewtwo DLC. Sadly, some people ran into trouble and could not play as Mewtwo on online battles. A few had problems with single player as well and messed with the Global Smash Power rating, which caused the system to falsely players as attempting to cheat and preventing them from joining in with online matches.
Nintendo has apologized and promised a solution to the problem, which is now available. A new update is available for both the 3DS and Wii U versions of the game, which is mandatory before playing online. This update has also shut down the workaround with custom moves that made for great YouTube content.
At least Mewtwo is fixed and just in time to be sold to the public.