The 35-year-old 'X-Men' actor did not name the movie part he was trying out for, but said he had to learn how to play several songs on the guitar and was massively unprepared for it.
Appearing on The Graham Norton Show, he told host Norton: "My agent suggested something that she thought was going to be great for me. I needed to learn songs and to play the guitar.
"I said, 'No problem', but of course the day came and I was rubbish at all of that and I stood in front of them with my heart in my mouth and thought, 'I've got to get out of this', so I started to cry and through my tears said, 'I've just had a phone call. My mate has been knocked down, he's at the hospital and I have to go'."
The star was recently one of the major winners at the BAFTA Scotland Awards. He was the recipient of the Best Film Actor Award for his portrayal of a corrupt police officer in director Jon S Baird's dark comedy 'Filth'.
McAvoy will also be going bald for 'X-Men: Apocalypse'. He will take on the iconic Professor Xavier look for Bryan Singer's sequel.