This is the second episode to reveal some of Castiel's past, first being season 6 episode 20 The Man Who Would Be King.
In Judaism, the Ishim (Hebrew: "men", "personages", "personalities", "individuals") or Eshim (Hebrew: "fires", "flames", "sparks") are a class of angels said to be the closest to the affairs of mortals. They are composed of fire and snow, and are described as the "beautiful souls of just men" who reside in the 5th Heaven.
All the angels in Castiel's flashback have the same vessels there as they do in this episode all except Castiel who left his vessel and over 100 years later he found another vessel (in season 4. 2009) so he could help stop the apocalypse and he has had the same one ever since.
Actor Ian Tracey, who plays the angel Isham, also appeared in a season 7 episode ("Adventures in Babysitting") as hunter Lee Chambers.
Dean calls Lilly "One Eyed Willie" this is a reference to Goonies. One Eyed Willie is the pirate who hid the treasure the Goonies are looking for.