What's the crack? What's the craic?
Officialy: What's the craic? Craic being an Irish language word for good times/ gossip/music/ drinking/ debauchery of any kind/ or good clean fun.
Not specifically linked to crack of the crack-cocaine definition.
If asked this question by an Irish person, you are expected to give a reply which includes information on how you are, what you are doing, where are you going, with whom are you going there, have you any interesting gossip one might like to hear about, and so on. It is a question to which there are many possible answers, and it is used with great frequency on the Emerald Isle.