Here is a statement from Coppola as he recalled the unique casting process for the film:
"We gathered all the actors on a soundstage and had them read for different roles."
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The clips shared in his post show various actors auditioning for roles they ultimately did not get. The movie, like the original novel, follows the story of rival teenage groups in rural Oklahoma: the underprivileged Greasers versus the affluent Socs. Howell portrayed the main Greaser character Ponyboy, while Macchio played his close friend Johnny. The ensemble included Lowe as Soda Curtis, Swayze as Darry Curtis, Dillon as Dally Winston, Estevez as Two-Bit Mathews, and Lane as Cherry Valance.
Here's another statement from Coppola about the experience:
"It was interesting because each of them observed their competition, but instead of it turning negative, it fostered a positive environment. They developed mutual respect and camaraderie. The outcome was outstanding and reminded me of my days as a camp counselor."
Source:Yahoo