I'm not joking.
I was playing Sakura Wars: So Long My Love and I pause the game and go get a snack. When I come back, the Gamepad (was playing using the Gamepad screen) was dim and the lights on my Wiimote were off, as happens when you idle for a couple of minutes.
So I press the A button on the Remote and...the lights flash on the remote (all four of them, so it wasn't a weak battery) and nothing happens.
I try again and again, so I realize: the fucking Wii Remote has become desynched from my system.
So I decide to just turn off the system, since I'm using the GamePad, I'd presume I can just press the power button. Apparently, when using Wii-mode, you can only use the GamePad to turn off the actual pad, not the system.
So I use the power button on the system. I hold the button for literally 30 seconds and IT STILL DOESN'T TURN OFF.
I literally had to UNPLUG MY FUCKING WII U TO SHUT IT OFF.