It’s difficult to not let a smile creep onto your face whenever the titular character of Frank (Michael Fassbender) comes on screen in Lenny Abrahamson’s quirky Sundance standout “Frank.” Along with having a normal fit body, he wears an oversized, painted, artificial head, complete with big, wide, blue eyes and a small, oval mouth resembling a fish’s. 

With the head on, Frank always looks like he’s in a constant state of astonishment. He’s the leader of an experimental pop band, but wearing this head is more than just an attempt to have an original appearance as a musician. For Frank, wearing the head is a lifestyle: He insists on wearing it even in the shower.

So why does he wear it? Well, he’s crazy. If that sounds like a spoiler, it really isn’t. While Frank never directly addresses it — when confronted about it by someone early on, he responds by saying all faces are weird — it’s pretty easy to figure out. 

We learn that Frank had an abusive childhood and spent time in a mental institution. This oversized head is his way of coping with the world around him. He’s only truly alive when he has the head on, and it’s easy to see why his band mates, who have their own issues, fawn over him. He’s enthusiastic and encouraging, almost spiritual. But he’s also obsessive and unstable. 

He’s a peculiar and entertaining character to watch, and Fassbender, having to perform without his own face, gives an endearing, spacey performance. His muffled, slightly slurring voice is perfectly suited to such an eccentric person. 

Unfortunately, the movie around him isn’t quite as eccentric and inspired; instead, it’s a relatively one-note tale of weirdos who don’t want to be normal and the normal outsider who threatens their lifestyle. 

Part of the problem lies in the fact that Frank and his merry band of misfits are seen from the point of view of that normal outsider, Jon (Domhnall Gleeson), a struggling musician who becomes the band’s keyboardist. Gleeson is appealing in the role, but the character is nothing more than your typical, dorky, indie-film protagonist. Without a second thought, he goes to live with them on an isolated compound out in the woods to help record their album. 

In their almost-blind devotion to Frank and his “genius,” the band resembles a cult, albeit a dysfunctional one. There’s constant bickering among them, and certain members threaten to kill themselves or leave the compound, all while they try and make music through unorthodox ways. At one point during a playing session, Frank makes everyone pretend to be chickens and pretend to lay invisible eggs. 

The supporting characters, by and large, remain underdeveloped. Maggie Gyllenhaal’s cold and intense performance as Clara — who doesn’t like Jon being there — starts to feel especially narrow and inauthentic. 

As the movie enters its homestretch, things only get more fatiguing. After weeks of recording videos of the band and uploading them to YouTube, Jon lands them a gig at South By Southwest, one doesn’t go so well. The picture then becomes a schlep, and even the trajectory of Frank’s character becomes clichéd and uninteresting. 

Fassbender gives a great performance, and it never gets tiring watching him and his unusual head interact with the environment around him. But, in the end, Frank’s an entertainingly bizarre character in need of a better movie.