Miis appear as background characters and one Mii stars as the main character in the game Nintendo Land: Balloon Trip Breeze. As a playable character, your Mii is blown around by the wind, which is started by sliding anywhere on the Wii U Gamepad touchscreen. Background Miis can be seen on Rest Islands and in Rest Houses, and don't serve any purpose besides decoration.
The playable Mii wears a costume that looks like the Balloon Fighter as he is seen on the Famicom box art and the Vs. Balloon Fight artwork. Background Miis wear a white shirt and overalls of their favorite color. As a background character, they throw confetti when you beat a level, and wave when you land and take off. When tapped, they throw their arms back and jump slightly. The playable Mii is selected when you walk into the gate seen in the plaza. Background Miis are randomly selected from the Miis on your system.
In Wii Fit U, Miis are also used as playable characters and background characters. In one game, Trampoline Target, once you jump high enough you can see two Miis (In a more proportional form) flying with three Balloons (one red, one blue, one yellow) each and bouncing into each other. The Miis' poses are also based off of the Balloon Fighter's pose when flying.