7. Agent Phil Coulson & Wanda Maximoff
A passing comment in the Avengers movie from Tony Stark who, when asked by Steve Rogers if Phil Coulson was married, replied "there was a cellist", led many keen-eared and knowledgeable fans to believe that this was a reference to Wanda Maximoff, the Scarlet Witch, who has been known to play the cello in the comic books. As a result, the revelation that Wanda Maximoff is set to be a character in Avengers: Age of Ultron has set tongues wagging about whether or not a history between her and Coulson will be revealed on screen. Of course, Elizabeth Olsen who will be playing Maximoff is only 24 years old, while Clark Gregg who plays Coulson is 51, so it seems unlikely on the surface. However, given the magical powers of the Scarlet Witch, it's entirely plausible that she might be preserving her youth through magic (and given that rumours are rife that she was the person responsible for Coulson's resurrection from death, her power - if that is the case - is obviously very potent). If indeed they do have a (storyline) past together, it will be great to see them interacting in a movie.