Grease Dance
50 Achievements
PS3
Full House
Complete a song with two Dancers and two Singers (Dance Mode)
22.2%
How to unlock the Full House achievement in Grease Dance - Definitive Guide
leptonic
This trophy requires two PS Moves and 2 mics; the PS Eye Camera can help using it as mic, but not for the controllers.
Just select Dance mode, 4 players select any gametype you wish and any song. Complete it and the trophy will pop at the end in the results screen.