Domhnall Gleeson has revealed it wasn't easy getting into Frank Sidebottom's head in Frank.
The Irish actor was required to don the fibreglass headgear, normally worn by Michael Fassbender, in one scene in the black comedy, which is loosely based on writer Jon Ronson's experience performing with the mask-wearing creation of comedian Chris Sievey.
"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," he admitted.
"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," he added.
Michael Fassbender stars as frontman Frank, who hides his identity inside a massive cartoon head, just like Sidebottom's, while Domhnall plays keyboard player and aspiring songsmith Jon.
"I hadn't heard of Frank Sidebottom, and in a way, I don't think that was any harm," Domhnall said.
"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."
Domhnall, who has been cast in the new Star Wars film, Episode VII, added: "So it didn't really matter that I didn't hear of him before."
:: Frank is in cinemas now.