The River Song Paradox

A Paradox in which a Time Traveler from the future meets a friend in the past before that friend has met them, and subsequent meetings occur out of order.

The "River Song" Paradox, according to the Chinese Bootleg Edition of the Hitchhiker's Guide to the Galaxy, has a "Smart End" and a "Stupid End." The person with more knowledge is on the "Smart End," and the person with no clue WTF is going on is on the "Stupid End." Of course, the nature of the Paradox being what it is, at some point in their shared timeline, the one on the "Smart End" will swap places with the one on the "Stupid End."

This is especially noted to happen to Time Lords, and other races with similar powers over time.