It's called photosensitive epilepsy, and for those who are susceptible, a strong sensory overload such as a movie's flash effects in the dark theater, can induce a seizure.
In "Breaking Dawn: Part One," the film's graphic birth scene has a bright flashing of red, black and white, just like a strobe light.
According to an ABC News report, several movie goers have reported convulsing, difficulty breathing, and body tremors during the scene.
Some passed out, requiring help from paramedics.
These episodes are rare, but they're not unheard of in a movie theater.
Some seizures were also reported last year by people who saw certain special effects in the movie "Avatar."