Alternate laser hockey paddle
If you push A and B together you can switch to a different circular paddle before the timer starts.
Do the following to unlock the medals.
Billiards: Get at least 63 points.
Charge: Get a score of 325 points.
Find Mii: Get to stage 100.
Fishing: Get over 2,500 points.
Laser Hockey: Get at least 16 goals and win the match.
Pose Mii: Get over 1,000 points.
Shooting Mange: Get over 600 points.
Table Tennis: Return the ball more than 200 times without missing.
Tanks: Complete the first 20 levels to get the Gold medal, then play through the game again, which now has 100 levels.
Leave your Mii alone for some time and it will fall asleep, activating new music and a screensaver.