A lot of the time I just wanted to use the Wii U to play Wii or transferred VC games. The gamepad keeps turning on when I start the Wii U. Is there a way to disable this?

Yup, superpowers.

The console and GamePad are non-detachably connected to one another. So if you want to play, the GamePad has to be on, even in the case you don't want to use it. But it turns off, when you switch to the Wii-Mode, isn't it?

What happens if the Gamepad is out of battery, or not in range? I haven't thought of trying this. The Gamepad could also be linked to another Wii U, but that would be harder to test (who has two Wii U's?)

The GamePad is essential, so you have to use the charging cable if you want to play with no battery. Unless you play a Wii-Game because there is no GamePad support (not yet).

I just picked up my GamePad to find out ... no charge. I was rearranging my entertainment center yesterday, and I must have accidentally turned on Wii U at the console and didn't realize that the GamePad was also on. Anyway, so I picked up my Pro Controller, and it not only starts the Wii U console but it can get you to and into a game that supports the Pro.

I have also used my Wiimote to operate my Wii U when the gamepad is dead, mainly Netflix though.

I can't turn on my Wii U without my GamePad, because my account is locked, and I'm the only one with an account on it.

@rancidvomit86 won the thread. Everybody can go home now.

To be honest, Nintendo should address this. Allow Wii U bootup without requiring the Gamepad to be turned on (and allow the Wiimote to switch between the channels and the Plaza if it doesn't already), but when trying to access a Wii U feature, whether that be games, apps, etc., it will check if the Gamepad is on and connected. If it isn't, then it'll wait for you to turn it on (or it'll turn on by itself?) and get it connected before it can go any further. There is already such a check in place for accessing the Wii mode, so I don't see why it can't something similar the other way.

You can turn the Wii U on with the Wiimote.
You navigate around the Plaza and channels with the Wiimote.
You can turn off the Wii U GamePad's screen and sound.
...What else?

Let me clear up a common misconception for past and future replies. Turning off your Gamepad's display is NOT the same as turning off your Gamepad. Turning off the display will continue to drain the Gamepad's battery life, which it doesn't have much of to begin with.

To answer your question: you can turn off the Gamepad by taking it out of range of the system until the link between the two is severed. From there you can turn off the Gamepad manually while still allowing the system to be on. You can then control the Wii U using a different controller. Personally, I have only tested this with the Wii U Controller Pro and I was able to boot up Monster Hunter Ultimate and play just fine, but at some point it will attempt to try to turn on the Gamepad again so you might want to keep it out of range.

You can also turn on your system using an alternative controller while the Gamepad batteries are dead.

Ah, that shouldn't be too hard to take the GamePad out of range, thanks.

Yeah, take it out of range, that's what I do everytime I play Skylanders Giants. Start the game first (or else the game turns it back on) and then take the Gamepad out of range to turn it off.