Why is the 'You know nothing Jon Snow.' a meme? Like, why that quote in particular?

That's not my actual question though... that's just for any old passerby. My actual question is :

"Whose death rocked you the most?"

For me it was the twirling staff guy with the sister who was fighting that really big guy as Tyrion's proxy. I honestly never saw that coming and was super shocked.

Unfortunately friends on facey spoiled the red wedding... I didn't know the details but I knew something bad was going to happen, so that was a shame.