The Human Centipede star had to agree to horrific condition in order to land the role

When it comes to properly gross horror films, there’s no doubt The Human Centipede is one of the first films that comes to mind.

It’s been well over a decade since the first movie landed and yet it still makes people wretch at the thought of it to this day.

The 2009 film follows a deranged German surgeon who kidnaps three tourist before conjoining them surgically from mouth to anus.

With it being such a horrific concept, it seems to make sense that the actors would have to agree to some horrific conditions in order to land their role.

And Ashylnn Yennie, who played Jenny in the first film, has spoken about one of the particularly bizarre ones.

During a convention appearance while promoting The Human Centipede 2, she spoke to Ravenous Monster about the audition process for the films.

While she said she’d ‘earned her stripes’ for the second film so ‘thank god’ didn’t have to audition again, the initial auditions were on the crazier side and a little ‘hilarious’, apparently.

Yennie in the 2009 movie. (IFC Films)

Explaining it can actually be seen on the bonus clips on the original’s DVD, she said that during the audition process with co-star Ashley C. Williams, the pair ‘actually had to get down on all fours’.

Yennie continued: “I was behind Ashley and then at one point she was behind me. And Ilona [Six, the film's producer] took pictures of just our eyes to see if we could convey that kind of terror without saying anything.”

The actor added that during the audition there was also ‘of course the screaming and stuff’.

And the whole eye stuff was something the stars really needed to excel at.

Williams previously spoke about that part of the role being what proved most difficult for her.

She told the Guardian: “I knew that acting with my eyes would be a real challenge. For filming, I went to Europe for nearly two months when there was still no script in place, so it was a real leap of faith."

They did the audition together. (Instagram/ashleycwilliams)

But the one thing people typically want an answer for is quite unusual.

Williams said: "The number one question I get asked is did anyone fart in my mouth? No! We were very respectful of one another, and the suits were layered so we weren't even close to the other person's butt.

"The infamous scene where the character at the front of the centipede has to relieve himself was filmed in one take and took 10 seconds. It was easy but I was grateful Tom didn't film it for longer than he had to."

Now surely a fart in your mouth is something you’d end up showing with your eyes.