Olympic Games: London 2012

You will need 2 controllers for this although you can do it by yourself. From the main menu go to Party Play and then choose any of the challenges. I personally chose the 1st challenge and earned the trophy on the Javelin section. Both athletes need to earn at least half of the goal amount in order for the trophy to unlock. For example on the javelin event you need to get a combined total of 170 metres to earn the 3 stars, so you need to get at least 85 metres with each control pad. Easy enough.