Speaking to The New York Times, Ben Affleck has revealed that while nun costumes and batsuits and whatever that Argo hair was are all fine, the one thing he will not put on his head is a Yankees cap. So, when director David Fincher asked that Affleck's character wear such a vile hat for Gone Girl, it was apparently a point of contention. Much as Meryl Streep will only ever wear a Celtics jersey, lest her bros give her wicked shit, Affleck's commitment to craft runs only as deep as his commitment to sports allegiances, and he refused to allow the character he was playing to wear the New York cap.
"I said, 'David, I love you, I would do anything for you,'" the lifelong Red Sox fan recalled saying before getting to the really douchey part. "'But I will not wear a Yankees hat. I just can't. I can't wear it because it's going to become a thing, David. I will never hear the end of it. I can't do it.' And I couldn't put it on my head."
In the end, a compromise was reached between director and actor-who-will-never-play-a-Yankees-fan. While Affleck was not allowed to wear a Sox cap, as seen above, he did at least get a step down to wearing a cap of lesser Boston rivals, the Mets, in exchange for wiping off his blue-and-red face paint.