Frank wears a giant papier mâché head, all the time. He is also the frontman of weirdo, outsider music group Soronpfbs (that's not a typo), in which he is given to proclaiming random statements, typically based on the environment around him. He's shown to be musically gifted in an inherent, natural way, something that you'd expect goes hand-in-hand with the fact that he's the kind of guy who wears a giant papier mâche head around the clock.
Fortunately, director Lenny Abrahamson is smarter than that. This is the sort of small movie that does well at Sundance that would be given to the armchair psychologizing around mental illness that many of its ilk fall prey to. This is one of the clichés the film avoids, along with many others, which is why its such a pleasant surprise, even if it is often an unpleasant experience to watch it.
Another pitfall Frank skips over is to under-characterize its protagonist in an effort to make him more likable. But we see over the course of the runtime that Jon is not just a fortunate tagalong who is our entry to the film's strange world, but rather that he is an interloper who wants to ride on the coattails of the patently more talented than he. Jon is ambitious—he constantly tweets, blogs and posts about himself in a mercenary and successful effort to increase his brand—but he has no real ability as a musician. He was simply in the right place at the right time, which lead him to join the band. It also helps that Frank is impressionable and easily excited, so Jon's mere pleasantness was probably enough to convince the leader he should be in their ranks.
The supporting cast has plenty of interesting, quirky characters who revolve around Frank, but the film sidesteps sacrificing their specificity in favor of likability. The Frank-whisperer in the group, Clara, immediately takes a dislike to Jon, not because she's jealous that Frank enjoys him, but because she can see right through him. Don, the erstwhile keyboardist and current manager, seizes Jon as an opportunity, seemingly to take him under his wing, but leaves him defenseless in the presence of other, stronger members of the group. The guitarist and drummer can tell that Jon is shit at music, and put him off accordingly.
Frank seems like a sort of pessimistic rebuke against the boundless optimism of a movie like Cameron Crowe's Almost Famous. It was based on a newspaper article by Jon Ronson, who wrote about Frank Sidebottom, the alter-ego of musician Chris Sievey, who donned an almost identical papier mâché head. Crowe's screenplay engaged with the experience of a teenager who yearned to be a music journalist, based on Crowe's own experiences. You can see the skeleton of Almost Famous in Frank, except with all the color drained out and with a specifically dour, British sensibility. If you're looking for a tonic to the sunny flavor of a film like Almost Famous, you can wash it out with Frank.