Jack has grown fond of you and Castiel. He likes to think of you guys as his parents and Sam and Dean as his uncles.

Right now you and Castiel are on a case together and you brought Jack along. Jack is supposed to be in the car as you and Castiel act as FBI and ask the local sheriff some questions. After you guys do that you go back to the car to see Jack gone so you start looking for him before you find him by an alleyway petting a cat. He looks up at you guys with his cute little grin "I found a cat"