There are 10 original crew members in the game, and you start with 8 unlocked. The last two crew members are unlocked via Crew Challenge. You must gain the respect of each crew by getting at least 16 stars on their songs, then 4 songs on their final challenge. Doing this for each crew will unlock the Glitterati crew. Once you've unlocked them, playing their songs will count as dancing with each of the last two crew members, and the achievement will unlock after you've played a song with each of them.