Wii U

Maybe get a better router and/or ISP subscription?
Or at least cut off the amount of computers/phone's/consoles/handhelds/etc. from your router?
 
I have like three or four devices on my router, but I only use three. One computers barely being used. And the last time I played the game was a month ago.
 
It also depends on what router you have.
Over here, we have 4 computers, 3 3DS's, 3 Wii's, 2 phones, and 2 back up units connected to the router, which is a total of just 14 devices, but we also use switches, so it isn't that much.
Also, we have a subscription of 20 Mbps down and 2 Mbps up (Megabit per seconds, Megabit is not Megabyte), and the router can take up to 1 Gbps (Gigabit per second, Gigabit is not Gigabyte).

Maybe your router or subscription would be some lower?
 
You had a fog on Mario Kart Wii?
That doesn't have anything to do with connection, more with some kind of hack on your side.
 
Than it is the connection after all.
 
I won't say it is or not, until it's officially known.
I mean, they did a great job with the 3DS, by requiring only one Friend Code, instead of thousands of Friend Codes, but chances are high to be a Friend Code system too, more to be compatible with the 3DS.
 
Derp what?!
StreetPass doesn't even exchange Friend Codes, it only exchanges your view-only Mii's, and you can play the 2 games in the StreetPass Mii Park. Nothing else.
To really exchange Friend Codes locally, a function in the Friend List has been added, a side of the Internet option, so you won't need to exchange them by hand.