The dialogue was mostly improvised by all actors, as the script only contained outlines of the discussions, not actual lines.
The patrol car appearing during the second scene was not scripted, it was a coincidence that they drove in the shot so the actors improvised around it.
All of the movie was filmed by hand, no Steadicam, no tripods, no cranes.
None of the actors were professionals, they were all friends of the director.
The apartment the third scene was filmed in was so small, the rest of the crew had to hide behind the kitchen door and duck while the character is in there.