At one point in the movie (around 26:05), Sara (played by Jenny Lewis, says to Derek (Leonardo DiCaprio), "Leo, man, chill". Derek and Amy (Amber Benson) were having a heated discussion in the movie but in real life, the two actors were known to not get along.
Near the end before Derek kicks over the table in the bar he is mouthing words but we don't get to hear what he is saying.