There you go. There's something Anger could say. And then one of the others could react to that. So forth. Presto! An RP.
And I am not being sarcastic here. I could literally write a Multiplex RP around Anger saying "blow me" to someone.
They would be distinct personalities, I believe. In fact, in most multiple personality disorders, the different personalities don't always know of the others. but yeah.
Just remember folks, not all good RP's require cussing.