"This kind of crazy event...." I agree with Tony about "social slots" - it's not a phrase used by native speakers and so the meaning would be unclear. I'm not really sure what it means.

One way to say it better is: Such a crazy event has never happened before in the world of social slots on Facebook! But "in the world of social slots" sounds a bit strange too. I would rephrase it like: Such a crazy thing has never happened before on Facebook.