What is The Cha-Cha?

Sylvia Fay, “Goodfellas” Extras casting director: We’ll give you a part in the movie.
Johnny “Cha Cha” Ciarcia: Read my lips. I don’t give a shit about a part in the movie. At ten bucks a head [for the extras used in the Copa scene], I figure you owe me $4,000. Just give me the $4,000 and I’ll be happy. And a casting credit.
Sylvia Fay: I can’t give you a casting credit, I can’t give you the $4,000, but I could give you a part in the movie.
Johnny “Cha Cha” Ciarcia: I says “As long as it pays $4,000, we got a deal.” Two weeks later, I get my check in the mail. It was $1800. I called up Warner Bros., I said, “My deal was for $4000. If I don’t get the balance of my money, I’ll be on set tomorrow and I’ll break all the cameras.”
Warner Brothers: Mr. Cha Cha, we apologize. You’re right! Accounting made a mistake.