Not only did God apparently leave an escape hatch for humans in the event of one turning up in purgatory, but he also created ways to open its gates for some reason. Crowley and Castiel manage to open the door to purgatory when they team up to mine souls.
Supernatural: 10 Episodes That Are Actually Terrifying
8 "Skin" - S1, EP 6.
7 "Family Remains" - S4, EP 11.
6 "Asylum" - S1, EP 10.
5 "Soul Survivor" - S10, EP 3.
4 "Everybody Loves a Clown" - S2, EP 2.
3 "Bloody Mary" - S1, EP 5.
2 "No Exit" - S2, EP 6.
1 "The Benders" - S1, EP 15.
