After collecting all of the minigame medals and the 98 silver and mega pins, you will receive a message about the legendary Pokemon. The Mystery Cave's entrance will be open one last time. Inside you will see Groudon and Kyogre, which will now appear in the Pokeball Throw and Find the Pokemon minigames. Their pins have a golden border. After collecting them, the game congratulates you and sets off fireworks around the island.