Dean had a dog once.
He found it as a puppy under the Impala, and it was as loyal to him as he was to Sammy and his father. It was supposed to be Sam's – it was Sam's begging that let them keep it – but it attached itself to Dean after a week and Sam was busy with other things by then, anyway.
It went with him everywhere – after he trained it to keep silent, even when there were scary monsters. Dad put up with it because it could find the monsters.
It was eleven months old when it found its last monster.
Dean had a dog. Once.