Sheen was a huge fan of Stone’s scripts for “Midnight Express” and “Scarface,” so he was invited to work with the filmmaker. Unfortunately, he didn’t exactly blow Stone away during his audition. As the actor told The Guardian on the oral history of “Platoon”, “Oliver said I was ‘too polite’ and needed to do more work.”
Luckily, Sheen had two great performances down the road in Penelope Spheeris’ crime drama “The Boys Next Door” and the coming-of-age drama “Lucas”. Stone was impressed enough to give him the role, but he had one final condition: Willem Dafoe, who will play Sheen’s Sargent and sell the mentor, must approve.
If this was some kind of obsessive ritual, Dafoe wouldn’t have gotten the memo. “I didn’t meet Willem until we went to the Philippines,” Sheen said. “He ran past me in our hotel and hugged me. Then Oliver came up to me and said: ‘Willem dug ya.'”
Dafoe’s instincts were discovered. Sheen deeply sympathizes with the idealist Taylor, in her own way. We see the frenzy of the fight through his innocent eyes (and his somewhat overbearing voiceover). He’s the perfect spectator substitute, and it’s still Sheen’s second-best performance.
https://www.slashfilm.com/985354/charlie-sheens-platoon-casting-depended-on-the-opinion-of-willem-dafoe/ Charlie Sheen’s Squad Acting Depends On Willem Dafoe’s Opinion