Wow. Just another incredible episode by GoT. This is by far my favorite season of the series, and we're only halfway through! So many things in that episode to talk about:
First, what incredible storytelling with the Hodor narrative. Martin has had that in his head since the beginning, and even being a non-vital component of the overall story, that was just an incredible narrative with how it was set up and played out. However, the philosopher in me wants to poke holes in the story due to its reliance on the grandfather paradox, though I'm not sure how relevant logic/metaphysics is when we're also talking about flashbacks via "greensight" in wargs.

Second, this is the first mention of the Children creating the White Walkers from Man, isn't it? Talk about a backfire! I thought that was a very interesting part of the episode, because I was under the impression that the Children were fighting the Walkers long before the First Men even came over to Westeros.
Third, did anyone else catch yet another hint confirming R + L = J?? When Little Finger was leaving and said "HALF brother." Yeah, the "half" part wouldn't matter, that is unless the other half is also Targaryen.
So, yeah, what an excellent episode. There was also a recent fan theory that emerged after the Tower of Joy scene that theorized that Bran's meddling in the past actually caused most of the events emanating from the Mad King. You can read about it here:
http://www.nme.com/blogs/nme-blogs/game-of-thrones-season-six-time-travel-paradox-theoryAfter this episode, that doesn't seem so crazy, huh? I'm really interested to see where they go with the Bran storyline from here on out. He was supposed to be the weapon to stop the White Walkers, but I'm not sure how that works out now. I'm guessing the time travel/flashback/manipulating the past stuff is going to play a role, because there's a reason that the Three-Eyed Raven took Bran there to see the Hodor stuff right before he was killed.
Though there is some contradictory stuff there. In the books, the Three-Eyed Raven told Bran, "The past remains the past. We can learn from it, but we cannot change it." But isn't that exactly what the Hodor situation was - the future influencing the past? It'll be interesting to see where this goes from here.
EDIT: So I just read something that the reason he was able to manipulate the past was because he was "greenseeing" while also "warged" into Hodor, which created some sort of connection that affected Hodor in the past where Bran was "greenseeing." My brain hurts lol