There Was A Hint Of Jon's True Parentage In Season One

HBO

Before it was confirmed at the Tower of Joy that Jon Snow is actually the son of Lyanna Stark and Rheagar Targaryen, there was literally writing on the wall. In the season one episode "Cripples, Bastards, and Broken Things," Jon Snow and Samwell Tarly are scrubbing the table in the dining hall.

When Jon mentions that he doesn't know who his mother i, you can see the letters "R" and "L" carved into a pillar that Jon is standing next to. It's an early yet subtle hint that Rhaegar and Lyanna are his real parents.

Did you pay attention to how the main characters died during the Red Wedding?