lol so that's why XD
you see, when the other player for example gets poisoned you have to flash the colored ray (forgot what it's called) on them, or else they'll accidentally infect the other players and while poisoned the controls will be reversed!
and when someone gets stuck by objects (drain/carpet, pot..etc) you have to use the vaccume you know
I've finised Dark Moon 100% and unlocked pretty much everything in story mode and online mode. I used to play online all the time to unlock fancy patterned ghosts. fun times ^^