To change paddle in Laser Hockey, you have to press A + B before the timer starts.
Complete the indicated task to get a platinum medal in the corresponding event:
Billiards: get at least 65 points
Find Mii: get to the 100th stage
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 over 200 times without missing