Game of Thrones season 6 spoilers below, of course.
Miguel Sapochnik directed the final two episodes of Game of Thrones season six, and he's been full of little details about how the show gets made. Most recently, he revealed the most challenging part of filming the season finale. In a series that deals with lots of sex, murder, and CGI to create special effects, it was a actually simple-seeming scene that proved difficult to film, thanks to certain time constraints.
According to Sapochnik, the toughest scene involved Grand Maester Pycelle and his demise at the tiny hands of eight tiny children working for ex-Maester Qyburn, also known as his "little birds." The reason it was so hard? The kids (thankfully) didn't know how to make a realistic stabbing motion with their stage knives:
When you give eight kids rubber knives and ask them to stab a blood bag, it’s not only somewhat disturbing to watch but you butt up against reality in which children don’t actually know how to stab something. Sounds silly but suddenly we found ourselves running out of time on the set with our eight kids and realizing that none of them really had much experience with stabbing and so it just didn’t look right.
It's also good that they respect child labor laws when working with children actors on set. Plus, they have to keep it light for the kids while doing a pretty grim scene:
The thing is at the same time as needing to describe and show them how it might feel, you don’t want to get into too much detail because they’re kids and the name of the game with kids is to make difficult scenes like this seem like fun and distinguish that they’re not real and why.
Unfortunately, the talented Sapochnik won't be directing any episodes in season seven. It's too bad, since his two turns this season, the "Winds of Winter" finale and "Battle of the Bastards," were both visual and emotional masterpieces.