Castiel:
To be completely honest, you weren't positive whether or not Castiel would find joy in caring for an animal. Sure... Cas had always shown a peculiar curiosity when it came to the environment and wildlife; however, he had never openly spoken about owning a pet.
Well... until he came busting into your room following a harsh thunderstorm, that is.
You had been busy researching, waiting for Sam and Dean Winchester to return home from their 'simple salt n' burn hunt' when Cas appeared before you. The angel's hair was absolutely drenched, his pants were caked with muck, and he was clearly hiding something underneath his trench coat.
...and it just so happens that the hidden 'something' was a sassy cat with long fur, bright yellow eyes, and mud covering almost the entirety of her small body.
At first, you had been hesitant to keep her, unsure of how Dean Winchester would react; but when Cas flashed a pout and placed the small cat on your lap...
...well, you had never been one to deny anyone, let alone a helpless animal, a warm place to sleep.
So... after a trip to the pet store and nearest veterinarian, you decided to call that beautiful cat, soon to be named Tally, your own.
Castiel loved Tally as if she were his own child. He always made sure that she was given plenty of love, had a full belly, and got the chance to play. Hell, whenever he had a couple of hours to waste, Cas would take Tally outside, wanting to watch as she chased after the different critters.
You can still recall the day that you had walked in on that dork of a blue-eyed angel having a conversation with his newest four legged friend.
"Tally," he had begun, rubbing underneath her chin. "I have read that cats bring dead animals to their humans... to the people that they love." Fading into the shadows, you listened intently, all the while doing your best to remain undetected. "...but, I do not believe that [Y/N] would appreciate me giving her a gift of that nature." he continued with a gentle sigh. "I love [Y/N] very dearly, Tally... and I really hope that [she/he] feels that same way."
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Sam:
If nothing else, you knew that Sam Winchester was an undeniable animal lover. He had always been the first person to approach one of the happy-go-lucky dogs at the park, loved dragging you into nearly every pet store, and even took the time to volunteer at the animal shelter during his few days off.
...and so, after a bit of sneaking around, you managed to find the absolute perfect gift for the younger Winchester brother.
Bailey was a handsome Golden Retriever with the softest reddish-gold fur, a playful attitude, and a love for any person that glanced in his direction. He was gentle and bright, adoring to learn new tricks, cuddle beside Sam on the couch, and giving 'kisses' whenever you felt down, in hopes that he might be able to cheer you up.
You can still remember the huge smile plastered on Sam's face when you first introduced him to his new furry best friend.
"Baby, I've already told you..." Sam had begun, laughing as you towed him in the direction of your bedroom. "You didn't have to get me a birthday gift."
"Too late," you sang, briefly pausing in front of the wooden door before beckoning for the younger Winchester to enter the room. Watching as Sam's hazel eyes widened when he opened the door, you smiled brightly.
"You didn't", Sam gasped, falling to his knees with a happy laugh when Bailey leapt off of your bed and bounded in his direction.
"Oh, but I did." you teased, eying the tall man as Bailey shoved his muzzle against Sam's hands, begging for a belly rub.
Peering upward, Sam leaned forward and placed a kiss to the top of Bailey's head, the world's largest smile playing his lips. "Have I ever told you how much I love you, [Y/N]?" he questioned warmly, his shoulder-length hair falling into his eyes.
"Every. Single. Day." you giggled, reaching out to rub behind Bailey's ear. "But... a reminder never hurts."
"I love you, [Y/N]."
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Dean:
FYI - [Y/P/N] = Your Pet's Name
You never once considered Dean Winchester's stance against pets to be a secret. Dean found animals to be messy and needy, either shedding all over the furniture, or begging for every ounce of available attention.
You had been pleading the elder Winchester brother for months, hoping to sway his strong opinion on the subject; though, you were almost certain that the task might be nearly impossible.
...well, until one of your many hunts led you both to an animal rescue shelter, that is.
His name was Sam, a fact you had found to be quite humorous considering he was instantaneously attached to Dean. He was a stunningly beautiful dog with soft mostly white fur, gorgeous dark colored eyes, and lean muscles perfect for racing around the bunker. You refused to leave without him; and though Dean was reluctant at first, he soon agreed.
Sam would be returning to Kansas with you and the older Winchester... well, as long as you could mutually decide on a new name, of course.
Hey... chasing after one Sam was difficult enough.
However Dean was a tad wary at first, he quickly grew to love [Y/P/N] full-heartedly. The green-eyed man throughly enjoyed giving his new furry friend belly rubs, and was quite fond of playing fetch until the bright Kansas sun disappeared over the horizon.
In fact, you can still remember the first time Dean had allowed [Y/P/N] to join you both on your bed.
"Alright, man..." he had begun, gently rubbing the patches of dark fur behind [Y/P/N]'s pointed ears. "I don't want any funny business. Got it?" With a quiet giggle, you leaned your head against Dean's shoulder, watching as [Y/P/N] gazed upon the muscular man with excited eyes. "You might be my new best bud..." he continued in a mock-stern tone. "...but [Y/N] will always be my number one.