Domhnall Gleeson has revealed that he had a few hiccups filming Frank, when he couldn't fit into the mask Michael Fassbender wears throughout the film.
According to Press Association, the actor said: "There was a scene where I was meant to slide on the head to see what it looks and feels like. It turned into quite a long scene. I wasn't really able to get it past my nose, because apparently, my head is quite big.
"No one else had trouble trying it on. People wanted to have a go. Everybody wanted to try on the head and do the funniest move - there was a little bit of that - but the only person who really made it work is Michael."
The About Time star added that he didn't know much about Frank Sidebottom, the musician that the character of Frank is loosely based on.
Gleeson explained: "I hadn't heard of Frank Sidebottom, and in a way, I don't think that was any harm. The problem we'll face with some people who do know Frank Sidebottom, is that they might come to the movie expecting it to be about him. That'll be a hurdle to get over, as it's not about him.
"It's in the spirit of one of his crazy songs, maybe, but there's no biographical connection with our Frank in the movie and him - apart from the fact that he wears a head."
Frank is in cinemas now, read our review here.
Domnhall Gleeson, director Lenny Abrahamson and Michael Fassbender