HUGE SPOILER ALERT: Game of Thrones. The most recent episode of GoT (Season 6, Episode 5) had a major metaphysical time travel element, revealing the stunning and tragic background of the future affecting the past affecting the future of the beloved character, Hodor.
I'm not going to say more so as not to ruin it, other than this: show runner David Benioff says in the episode summary
that when he and partner DB Weiss did a big story download meeting with creator George Martin, this was the most shocking revelation, resulting in them turning to each other "and being like, holy shit
I strongly beseech you to NOT watch if you are not caught up or have any inclination at all to watch this series at some point in your life.
Interesting tidbit: the episode was directed by Jack Bender, who happened to direct many episodes of the epic time travel series Lost.