The correct colloquial is actually "What up nigga". What's up my pals just sounds like some ignorant rich white kids trying to be hard who think they know how to talk slang...
In Darwin, it's also fun to make fun of the way the blacks talk. Once you've experienced a drunken conversation with 6 or more people and everyone is pretending to be a drunk+high black fella... you'll never be the same again.