Users on Smashboards.com, a Super Smash Bros. gaming forum, have experienced console-bricking errors after playing Super Smash Bros. for Wii U. YouTube user Trippy12345ify has posted a video (embedded above) of the issue.
The topic creator, DrRek, believes that this has to do with For Glory mode after experiencing "a horrible amount of lag (I'm talking 2fps here)." After quitting the match and then turning the console off, he then rebooted his Wii U six hours later, only to find a serious error about corrupted system memory.
The thread has other users who have experienced this problem as well, and Nintendo has not been able to provide any solutions to the issue yet. Apparently, this error is common with the Wii U, though the Updata Data for Super Smash Bros. has been the most recent culprit, causing the console's flash memory to become corrupted.
Just a warning: Reformatting the system as a solution has actually caused the Wii U to become unusable. If you still want to play Super Smash Bros., we suggest playing offline and staying away from For Glory mode for now until Nintendo can get a second patch out.