SPOILER WARNING!!! WATCH IN HD!!!
even though it's not confirmed yet, I truely believe that Jon is Lyanna and Rhaegar's son (and yes Rhaegar and Lyanna are my fav ship of the series).
here is a great summary of their story: http://www.myspace.com/adamthornhollowrec/blog/144839061
"And the mystery knight should defeat all challengers and name the wolf maid the queen of love and beauty."
"She was," said Meera. "But that's a sadder story."
- A Storm of Swords, pg. 283
Rubies flew like drops of blood from the chest of a dying prince, and he sank to his knees in the water and with his last breath murmured a woman's name...
- A Clash of Kings, pg. 706
He could still hear her at times. Promise me, she had cried, in a room that smelled of blood and roses. Promise me, Ned. The fever had taken her strength and her voice had been faint as a whisper, but when he gave his word, the fear had gone out of his sister's eyes.
- A Game of Thrones, pg. 43
Lyanna Stark: Eva Green
Rhaegar Targaryen: Orlando Bloom
Young Robert: Viggo Mortensen
Young Ned: Sean Bean ;)
clips from: Game of Thrones, Lotr, Camelot, Kingdom of Heaven, the Pillars of the Earth and Merlin