Imagine if a mysterious woman came up to you, told you that she was your wife from the future, helped you save the day, and then disappeared. Confident, smart, and a sharp shooter—that woman is River Song, the Doctor's wife. Conceived in the TARDIS (that's the Doctor's box—we'll get to it in a minute), River Song is human but with a Time Lord-esque understanding of the complexity of time and the ability to regenerate.

She and the Doctor have a relationship that's like every Rachel McAdams time traveling rom-com wrapped into one, except less cheesy, with less crying and more awesome.