Crackin means happening. Adding some kind of word that gives the word a sense of action - like a spinning wheel....something that is in a state of action ; you can say: what's crackalatin ? and this actually means "yo / hey, what’s happening ?!"
A sound from a pimp slap. Watch the Doggy Fizzle Televizzle where Snoop D-O-double Gizzle is Cap'n Pimp. He back hands them and it says "Crackalack", just like in the old Batman & Robin show.