The scene in the woods with James Woods and Vincent Kartheiser was completely improvised and involved Woods hitting Kartheiser repeatedly with his fingers. The gestures are so rough and sudden that you can hear each hit and see Kartheiser's genuine surprise, respectively. Afterwards, Kartheiser went up to director Larry Clark and said, simply, "I didn't know that motherfucker was going to hit me."
Director Larry Clark didn't believe that Vincent Kartheiser, then 18, was of a legal age for his role (involving nudity, sexual situations, and drug use) and wouldn't cast him until he was able to prove his age. Kartheiser was cast once he produced his driver's license.