Next week, the Cory Monteith tribute episode on 'Glee' will air in the USA (October 10) and the show's creator, Ryan Murphy, has confessed that it was an incredibly difficult one to film. 

He explained that they shot the episode, entitled 'The Quarterback', a few weeks back and it was so emotional for the show's whole cast:

"It was incredibly difficult to work on. It was very difficult to shoot. I mean, the interesting thing about that show is that those actors and the creators really, really loved Cory. The episode is called 'The Quarterback,' and you know Cory really was that, to that group of people and to me particularly. There was nobody on that crew that did not like Cory."

"It was rough. It was very rough. It was very rough with Lea Michele, but I'm very proud of it. I think the performances are quite stunning. People still are not over it. It's still very, very difficult. I've never seen a crew that you can't continue shooting because they've left the room sobbing. It was very hard."

Murphy added that he was also overwhelmed with the amount of people who expressed an interest in appearing in the episode:

"What I loved about it is, you know when you write something like that, there's no right way to do it, so we wrote it and we put people who were under contract to the show in it and a lot of the actors contacted me and said, 'I just love him so much, can I please be a part of it?' So we put those people in."