"When you cast, you are assembling an orchestra. The films are a symphony and each actor is a precise instrument. Each of them brought a dynamic, so it was really quite a banquet of different techniques, realities and chemistries," said the two-time Oscar winner for "The Shape of Water."
"It's like the '27 Yankees, man. It's murderer's row," said Ron Perlman, who comes out in the film alongside who he dubbed his "heroes."
Getting all those actors together creates something special on set, said Cooper.
"All these incredible actors...that's a lot of energy and when you have that much energy, magic can happen."
Set in the late 1930s, Cooper plays Stan, a man who shows up one day and joins the carnival world, soon realizing it could change his world.
"The key to this movie is Bradley. I cannot imagine doing the movie without him as a partner, and by a partner I mean, not just as an actor, director. We were dealing with a guy that understood the whole movie. He held it in his head," said del Toro.
"There are a lot of firsts for me in this movie as an actor, things... that I was always terrified to do. I don't think I've ever been so vulnerable," Cooper said.
Cooper plays opposite three acting powerhouses in Blanchett, Collette and Mara. Del Toro said those three female figures illuminate the "darkness" that is Stan.
"Everyone of us kept mining each scene we were in...and you don't know what's going to work or not, but it's all about the effort. This one was for the love of the game, period," Cooper said.
"Nightmare Alley" is rated R and now in theaters.
The Walt Disney Co. is the parent company of Searchlight Pictures and this ABC station.