According to director Alex Graves, it’s all because of Joffrey’s dead body (another strong performance by Jack) having to be in the scene for maximum awkwardness.
“I’m never that excited about going to film forced sex,” Alex thankfully reveals to the Hollywood Reporter. “But the whole thing for me was about dead Joffrey lying there, watching the whole thing. [Showrunners] David [Benioff] and Dan [Weiss] loved that, and I was like, I wanted to make sure I had Jack in there as much as I could. Of course Lena and Nickolaj laughed every time I would say ‘You grab her by the hair, and Jack is right there,’ or ‘you come around this way and Jack is right there.’”
We wonder if Jack also had trouble keeping it together during the scene. We kind of wish he had laughed on camera. A giggling dead body would have at least taken our attention away from, you know, the raping.