The mii qr codes will tell the 3ds what the mii looks like and ports it to your 3DS.
Here is a demonstration. http://nintendo3dsblog.com/the-reggie-mii-is-your-3ds-ready
So go and post away.
Also here are some Japanese people made http://matome.naver.jp/odai/2129879257320612101

I'll be sure to post mine when I finally get around to making one. _{But I'll need to make one for Pilotwings....}

Maybe I don't want people to play as Mii D:

Yeah, I'm with X. Mine'll be up when I can get my lazy behind to making one.
But don't y'all be stealing mah Mii now. O.o

How do you have a Mii code already? Japanese 3DS? And how did you make a code for your Mii? What does QR stand for? Can Mii's obtained this way be used for Streetpass Quest? (Probably not)

That's not a mii qr code.

I'm fairly certain that isn't a Mii QR code since it has 8-Bit Mario in it Is that a code readable by 3DS at all?

I'll do you guys a very awesome favor.

You wanted him, you got him. Are you ready?

IT'S THE REGGINATOR!

Now you're playing with power!

I already saved Reggie's QR code from that other site for future reference.

Lol, I wonder if you can use the camera to make miis of famous people by directing the camera at pictures of them.

Same here. I'm just sharing out the good stuff to all those folk who missed out on it.

Get at it.

Aha! Hatless Luigi! That pretty much confirms that there will also be a Luigi hat to unlock, but since Wario is wearing that god-awful knitcap, there won't be any Wario hat.

Can't wait to see how the exporting function works. If it's user-friendly and not made obsolete by other sharing functions i'll be sure to post at least one of my codes here.

@Tj92: I think these are fan-made Mii's, not official ones.

Hey guys! Aside from Reggie, Have there been any official ones???

Can't wait to get my 3DS so I can play around - I think the games should have QR codes in the game box of the main character of that game! That would be aces!

Here's mine.

Saved.

What happens if you scan Missingno.?