Every time you complete the daily brain training you will unlock minigames.
This also requires 1 day of Brain Age as well to unlock Umbrellas and Where Is The Meat? (Credit Shadow Kisuragi). This will pop after you've played the brain training 7 times. You can only play once per day.
You can adjust the date on your phone to get this quicker if you really want - set the date to a week ago, complete the brain training, exit game and change date forward a day. repeat several times and achievement will pop.
CAUTION - If you change the date to the future and pop the achievement then it may not be recognised by xbox.com