Flesh and Bone

Dean's trapped in Purgatory looking for his angel when a not so subtle kid in a red sweatshirt asks to team up. Dean takes Little Red Riding Hoodie underneath his wing as they try to escape.

Or the one where Stiles bargains with a witch to get sent to purgatory to save Derek and finds Dean instead. They work together to find a way out of Purgatory as they each look for their "person".