The character of Frank in Frank is based on Frank Sidebottom but not only Frank Sidebottom. His head, as you'll see in this image, is pure Sidebottom.
That's Michael Fassbender there, flanked by Maggie Gyllenhaal and Domnhall Gleeson. I could tell you what they're doing but then Jon Ronson would have to kill me. It's probably safe to say that this Frank is quite like the last Judge Dredd movie, however, in terms of how often you'll see Fassbender's face.
Frank is being directed by Lenny Abrahamson. His film What Richard Did is released in the UK this Friday - tomorrow! It's superb. Watch it.
And if you need some sort of background on Frank Sidebottom, I tried to help a little in a previous story. You know I did, I really did.