Mary-Jane in SpiderMan
She was one of the runner-up for the role of Mary-Jane. She confirmed it in an interview. I think she would have been perfect!
That is sad for a number of reasons:
1- because I don't particularly like Kirsten Dunst,
2- because I've just been watching Wonderfalls and Caroline is so likeable in it and,
3- because it would most likely have made her a star, meaning she would be in more movies etc.
On the other hand she wouldn't have been in Wonderfalls which would have been a pity.