Thanks, DeNiro! And you posted a tough one, given the Rat Parade in the Mafia over the last decade:

You might argue that Joe Bonanno was the first due to publication of his autobiography, "A Man of Honor," in 1983. Even though he'd "retired" to Arizona after the Bananna Wars, he still had influence in his former family. And though Bonanno had not formally flipped to the police, Rudy Giuliani, then US Attorney for the Southern District of NY, used Bonanno's book as the basis of the famous "Commission Case" that put most of the NYC Dons away for 100 years.

You might also argue that Junior Gotti, by pleading guilty to racketeering charges in 1998, was the first to "flip." But it's not altogether clear that Junior was really in charge of the Gambinos, or whether it was wishful thinking on his and his father's part. Also, the police found a ton of damning evidence at Junior's home that helped convict others. But whether or not he led them there deliberately, or whether it was just because of his own stupidity, isn't clear, either.

I'd say the first indisputable head of a NYC Mafia family who flipped while he was a Don was Anthony (Gaspipe) Casso of the Lucchese's.

Q. Which famous NYC Don ratted out a partner in a drug deal as a young man?