Would you like some spoilers to go with these spoilers? I'm just heating up some spoilers on the spoiler.

That hair, though. (HBO via Huffington Post)
That hair, though. (HBO via Huffington Post)

It used to be fun and hip to speculate about Jon Snow's parentage. But at this point if you're not sold on R+L=J, you're only deceiving yourself (or for some reason you don't devote huge blocks of time to reading Game of Thrones fan theories... in which case, how did you get here?).

"R+L=J," of course, obviously, as everybody knows, is the theory that Jon Snow's true parents are Rheagar Targaryen and Lyanna Stark. Now, as we all learned in elementary school, after Rhaegar was killed in battle by Robert Baratheon, the new king sent Ned Stark and Howland Reed to retrieve Ned's sister Lyanna Stark from the Tower of Joy. According to lore (aka nerds), Ned found Lyanna in a bed of blood, implying she might have just given birth. Her last words to Ned were "promise me," which most people have interpreted to mean "promise me you'll protect and hide the identity of my baby, this Targaryen-Stark hybrid who shall hereafter be known as Jon Snow."

Sources: Huffington Post