When Sonny's friends try to convince him to go to Houston with them, they argue there's more to the world than "Holland or Hamsterdam or wherever the f_____ you're from". This is a sly reference to David Simon's previous project, "The Wire", where a senior police official creates a "police-free" drug zone called "Hamsterdam" in Season Three. It's more telling as Sonny has had trouble with drug use in the past.