Reputedly, all LAPD officers and some civilian employees are issued a master key that opens the back door to any LAPD station house. These are called '999' keys.
The idea of an angel/demon cutting off their wings, dying in human form and thus returning to heaven/hell (as alluded to by Amenadiel) is also a major plot point in the religious comic fantasy film 'Dogma.'
999 is the emergency services number in the United Kingdom.
When Lucifer and Amenadiel are at the beach, they say it's because Lucifer and Maze fell there when they left Hell. In City of Angels (1998), angels gather on the beach to watch the sun set.