Matthias Ludwig was originally considered to play the role of Gin, but had to decline due to scheduling conflicts.
The young man sitting next to Billy offering him a joint is actually a cameo-appearance. By saying "Dude, I don't have AIDS" the actor is referring to his own role in the 2010 movie "16:30", in which he played a young man who is infected by HIV.
None of the actors has ever played any of their band-instruments prior to shooting. The 'Band' would practice the basic notes of their instruments shortly before the shooting of the scene began.
In order to guarantee each band-member's unique style and language, each of the four main screenplay-writers designated themselves to one of the band-members and mainly wrote their character's dialogue.
The scene which took most takes to shoot is the one after the flashback of Nadine and Vince's kiss, at the first party. A shot in which Vince's only line is "Oh yeah!".