Almost all of the dialogue was unscripted and improvised, from scene-by-scene outlines as instructed by the director. Likewise, a large bulk of the music was composed during filming, by members of both of the film's 'rival' bands.
The original singer of the Stuðmenn band (Gylfi Kristinsson) makes a brief cameo as a fishmonger.
In real life, Tinna Gunnlaugsdóttir, who plays the Stuðmenn singer's "dream girl", is his wife.
Both bands depicted in the film were real pop bands at the time (named Stuðmenn and Grýlurnar), and all the performers real musicians who genuinely play their respective instruments on screen, with none of them being professional actors. The all-female Grýlurnar band disbanded not long after the film's release, while Stuðmenn still remain active (as of 2016), though with slight changes of band members.