Joy (The Impossible Astronaut)

Joy was an American woman who worked in the White House in 1969. Emerging from a toilet cubicle, she saw a Silent. She assumed its face to be a Star Trek mask but when she looked away, forgot what she had seen. She looked again and repeated her actions, despite the warnings of Amy Pond. The Silent killed Joy with an electrical discharge from its hand, disintegrating her. A horrified Amy asked the Silent why it had killed her. It told Amy her name, having apparently killed her for no reason other than intimidation. (TV: The Impossible Astronaut)

Behind the scenes
Her name was likely chosen to create a sort of dark pun, where at first it seems as if the Silent was claiming to have killed her for pleasure.