Chris Colfer found the early days of 'Glee' to be a "very gruelling process".

The 34-year-old actor shot to fame as Kurt Hummel in the late 2000s TV series alongside the likes of Lea Michele, Amber Riley and the late Cory Monteith and recalled that the auditioning process was exhausting and that he and his fellow castmates all got "complete shock" when they realise how hard the dancing element of the musical show was going to be.

Speaking on the 'Drama Queens' podcast, he said: "The beginning of 'Glee' was a very grueling process. I think we each had four auditions. We had a casting director, callbacks, network, and studio.

"All in a row. We had to sing and act in those auditions. It wasn’t until we all showed up for the first day of singing rehearsal for the pilot that we realized that you have to dance in show choir, and none of us had ever danced before.

"And so that was a complete shock to us and to our bodies, because … it was never part of the audition process, and it was never written into the script.

"And, when I think of show choir, I think of like 'Sister Act 2', where they, you know, they kind of step touch, step touch, but it's really focused on the singing part. It was like the first time any of us had ever had to dance like that."

Chris - who has now carved out a second career as an author with children's books such as ' Roswell Johnson Saves the World' - also noted that the audiences of the Fox TV series seemed to blur the lines between the characters and the actors on the show, which he claimed was the "most challenging" part of being in the show.

He said: "What I didn't realise was when the audience found out that a lot of these experiences that they were watching were autobiographical of us, the separation between actor and character became nonexistent.

"And that was — that was probably the most challenging part of 'Glee', was having … millions and millions and millions of people think you were someone that you were not."