There's a cute little Sandra Bullock movie that I like to watch at the holidays called "While You Were Sleeping." She plays a lonely woman who works at a railway station, who has a crush on a handsome man who often passes through the train station, but she never speaks to him. One day, he is attacked and he falls onto the tracks and she saves him. As he is taken to the hospital in a coma, she (thinking of her fantasy life) says "But I was supposed to marry him," and the hospital staff take her words literally. Next thing you know, she's been introduced to his grieving and anxious family as his fiance, and she goes along with it, hanging out with the family, attending family events, and even going through the man's apartment. In the film, it's appealing, because Sandra plays such a good-hearted person and you understand that she's very lonely, and when the truth finally comes out, everyone forgives her and welcomes her into the family. But in real life, if a stranger posed as the fiance of a man she had never met who was in a coma, that would be pretty reprehensible.
