Actor Michael Fassbender revealed playing a musician in Frank allowed him to fulfil his rock star dream.
The Irish-German star, 37, stars in the title role of the oddball comedy about the eccentric frontman of a pop band who hides his identity inside a Frank Sidebottom mask. Frank was the comedy alter-ego of London musician and funnyman Chris Sievey, who performed wearing a large cartoon papier mache head.
"It was definitely an opportunity to live out a fantasy," he said at the film's UK premiere at London's O2 Arena.
"I like music a lot but my talent is pretty mediocre. I enjoy it, it's very much a part of my life."
He added: "Luckily enough, we had the luxury to rehearse for three to four weeks before filming so that was a great opportunity to jam together, learn the songs and gel together as a band."
The indie film, which also stars Domhnall Gleeson and Maggie Gyllenhaal and is directed by Irish film-maker Lenny Abrahamson, premiered on the opening night of the Sundance London film festival.
Fassbender - best known for starring in Steve McQueen's films, Shame, Hunger and 12 Years A Slave as well as playing Magneto in the new X-Men films - admitted it took time to adjust to working with the giant head.
"It's not really challenging - you get somebody else to go in the head and you stay at home," he joked, before adding: "No, it is me with the head.
"Initially it was kind of claustrophobic in there. There's not much one can see from inside the head - it's very restricted in terms of what's going on outside - but it was great fun," continued the actor. "It was very liberating and I felt quite mischievous whenever I put the head on so it actually lent to the character."
His co-star Gleeson poked fun at him, saying: "We just didn't get on."
The 30-year-old, the son of actor Brendan, added: "It wasn't that hard acting opposite a giant head. The truth of the matter is, he's amazing. He gave such an incredible performance that he was so present. And when he chose to keep quiet, it was terrifying because you don't know what's going on. He's a very generous man."
:: Frank is released in cinemas on May 9.