First, Pileggi said after he wrote the book "Wiseguy," the inspiration for the film, Scorsese tried again and again to reach him about making a movie, but Pileggi thought it was a joke from a co-worker.
"I never thought it was Marty calling,” Pileggi told the audience. “I was at New York Magazine at the time, and I’d get these little pink slips that would say, ‘Call Martin Scorsese.’ I thought it was David Denby, who was the movie critic at New York Magazine, so I didn’t respond.”
Also revealed during the special was that the iconic “funny how” scene between Liotta and Joe Pesci was actually a little improvised -- and how he went a little "off book" and needed to be brought back to the script a bit.
Finally, Sorvino said he almost quit the movie. He didn't like all the aspects of his character Paulie. So he told his manager before production began that he wanted to quit. He eventually changed his mind and everything else is cinematic history.