#15: Sienna Miller and James Franco
While filming Camille, Sienna Miller unexpectedly backed out of a kissing scene with co-star James Franco. Miller had been dealing with dental issues for some time, and just before the scene was set to be shot, she experienced a sudden flare-up. Though the specific nature of her dental problems remains unknown, they were severe enough to warrant a last-minute withdrawal from the scene.

Interestingly, Miller chose not to share the details of her decision with her fellow cast members, leaving everyone in the dark about her sudden change of heart. Her unexpected exit certainly added an element of mystery to the set that day.