The one sex scene in 'Girls' so explicit, even HBO refused to air it.

Lena Dunham’s Girls is known for it’s ground-breaking, no-nonsense and 100 per cent truthful (no matter how ‘gross’) portrayal of sex.

But there was one scene that even HBO – the network responsible for bringing us gore and sex for years – filed shows like Game of Thrones and True Blood – refused to show on screens.

In an interview with The Hollywood Reporter, the show’s co-creator, Judd Apatow, referred to the scene in question as a “conclusion shot”.

Um, excuse me... a what shot!? Image via HBO.

"It was actually cum arcing through a shot," Dunham clarified.

"And HBO said, 'If this is in the show, we could lose our license'. We were like, 'Oh my God, we've actually found the line at HBO'," Apatow said.

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While the team initially argued with the executives, they soon realised they "didn't need it" for the scene.

Even though that scene didn't make it to air, a lot of other sexually explicit scenes did, opening up conversations about things that are "normally hidden", said Apatow.

The show is known for starting conversations about sex. Image via HBO.

"So often you're not talking about a giant part of most people's lives because people don't want to portray it on film... and that opened up tons of stories that you're usually not able to tell," he said.

One scene in particular - between Adam Driver and guest star Shiri Appleby - caused a stir amongst viewers.

"When people watched that scene and said, "Is that rape?" I was surprised. To me, that was a fully consensual bummer of a sex scene," executive producer Jenni Konner said.

"But that was one where people got upset, and I was thrilled for the feedback because it was really thoughtful and emotional - it wasn't just this knee-jerk, "Oh, we did something else that pissed people off."

The sixth and final season of Girls airs on Showtime from 15th February, 2017.

Read the full interview with the cast and crew behind Girls here.