Spoilers. Big, huge, Game of Thrones spoilers the size of the giant ice wall that defends the North of Westeros.
Now that we've got that out of the way: This video by Alt Shift X is the clearest explanation yet of a popular fan theory that Jon Snow—sworn member of the Night's Watch and bastard of Ned Stark—isn't Ned's bastard at all. Maybe Ygritte was right: He really does know nothing.
Using thorough citations to A Song of Ice and Fire, the video makes a convincing case about the identities of Jon Snow's real parents and how his possible lineage would upset much of what we thought we knew about the game of thrones.
Too bad about that Night's Watch oath, though, eh?