Just Dance 3

Dance Mash-up songs are unlocked by earning stars by playing other songs. The first Dance Mash-up will be unlocked after earning 30 Stars, and another will be unlocked at 60 Stars. The Mash-ups you have unlocked can be accessed from the "Special" tab in the top right corner of the song selection screen.

To earn the trophy, just pick one of the mash-ups and dance the entire song nearly perfectly to earn 5 stars. The song from the name of the Mash-up will play, but the dance will rotate through dances for other songs. Just pay attention to the dancer on screen and follow the Pictograms. If you do not earn 5 stars on the first try, just play a few more times. When you finish a Mash-up with 5 stars, the trophy is yours.