(The reader is a Lamian Centaur. Lamian Centaurs were set by Zeus to be guards. The reader is a young foal, but was born with the mentality needed for this purpose. I hope you enjoy!)

(I know this is a Sans x Reader book, but this story has some moments with Swap!Papy. Papyrus will ONLY be added if there is a Sans to go with him. Like the title of this chapter. Example- Sans x ~~Reader x Papyrus. K?)

(C/C stands for Coat color, (H/C) stands for Hair color, and E/C for eye color.)

~Blue's P.O.V.~

Papyrus and me were walking around Waterfall after we went to Undyne's Lab. She was telling us about this weird creature she had seen on her cameras. I was extremely excited to find this creature and meet it. I wonder what it is, or what it looks like? Undyne could only see the shadow of the creature, but nothing else. 'Papyrus thinks it's just another monster, but I think it's a whole new creature. Maybe it's super strong, or it can move around really fast.' I thought to myself as Papyrus looked at me. I had stars in my sockets and was bouncing on my toes in excitement. "PAPYRUS!? I'M GOING TO FIND THIS CREATURE!" I yelled, running towards Snowdin.

~Author's P.O.V.~

As Blue was running around Snowdin looking for the new creature, Papyrus had teleported to the ruin doors as usual. He began his normal talk with the goat man behind the door, though the goat man brought up a very strange question in their conversation. "Have you seen a little girl running around recently?" Papyrus thought for a moment before asking, "Depends on what kind of monster she is. Can ya describe her for me?" Asgore, the name of the goat man, then responded back quickly after hearing Papyrus' question. "She is a centaur, not a monster. She's very young. I believe she is only four years old, though I don't know for certain. She has (H/C) hair and tail, plus she has a (C/C) coat." Papyrus takes in the information, remembering all of it, as well as suspecting the she is the one running around the Underground. "I haven't seen her, but I'll keep my socket out for her." Papyrus then hears a chuckle from Asgore. "Thank you Papyrus. Her name is (Y/N)."

Papyrus nods, though Asgore can't see it, and says his goodbyes. He then teleports back to his and his bro's house, but what he sees next makes him drop his lit cigarette. Luckily he dropped it on the snow covered porch and not the floor of their house. Blue was sitting on the couch with the young foal's head on his lap. She perfectly fit Asgore's description as well as being very large, but looked around four, just like Asgore said she looked. "Shhh. Please be quiet Papyrus. I just got her to fall asleep." Blue said in a surprisingly quiet voice.

(This is generally what you look like as a foal. You'll have a shirt on, but you get what I'm tryin' to say.)

Papyrus shut his mouth, which was quite agape, and walked quietly over to his brother and the sleeping foal. "Where did you find her, and why is she in the house?" Papyrus asked, sounding quiet rude, though he wasn't meaning to come off that way. "I found her running through Snowdin Forest. She was heading out of the forest and towards Waterfall. She's really skittish, but she's getting used to me quite quickly." Blue explains. "She's in the house because I don't think she has a family, or a home to go to. I couldn't leave her outside on her own! She could get hurt, not to mention taken! She's so little Papyrus!" Papyrus nodded and smirked at how caring his brother was for the little foal.

Papyrus was about to say something else when the foal started to stir in her sleep. Blue and Papyrus both looked at her as she stretched her arms and legs. The little foal then yawned and opened her eyes, revealing there bright (E/C) color. She looked at Sans and then turned her head and saw Papyrus. Since she had yet to meet Papyrus she flinched and hide in Sans' chest. Sans chuckled as his scarf was now being used to cover the frightened foal. "It's ok. Papyrus won't hurt you. I promise!" The little foal then looked at Blue and then back at Papyrus. She came out from under Blue's scarf and sat on the ground.

Papyrus walked over and pet the girls soft, (H/C) locks. She giggled at the feeling and slightly nuzzled into the feeling. This made both Blue and Papyrus chuckle. "I'm gonna head to Muffet's now bro. I'll be back later." Papyrus says and walks out of the house. Blue rolled his eye lights at his brother and walked over to the foal. "Hey there. How was your nap?" The little foal smiled and giggled. She stood up a little to fast and started to fall, but Blue caught her. "Easy there. You might hurt yourself." She looked up at Blue and smiled widely. "Tank you!" Blue blushed at her adorableness. (Not in a pedophilic manner!)

"You're so cute!" Blue says with star eyes. He then hugged the foal closely to himself and nuzzled her head with his skull. The foal just giggles and hugs him back. Blue then let's go and stops nuzzling her. "What's your name?" Blue asks. He had just remembered that he didn't know her name. "(Y/N)." (Imagine your name being said in an adorable four year old's voice.) She said happily. Blue smiled and still had the stars in his eyes, though they seemed to grow large. "(Y/N) is a perfect name for you! It's almost as adorable as you are!"

Blue then hears something that surprised him. A grumbling sound, and it was loud. He then noticed the little foal hugging her stomach. "Are you hungry?" The little foal, now known as (Y/N), nods sheepishly. Blue then zooms off to the kitchen to make (Y/N) the best tacos he's ever made. Blue then stopped as soon as he opened the fridge. There was no meat in the fridge, nor were there anymore taco shells. He didn't even have cheese, or any leftovers!

Blue then came back to the living room and had a slight frown on his face. "Maybe we should go to.... M-Muffet's." Blue said, not believing the words that just came out of his mouth. He knew Papyrus ate there a lot, so maybe (Y/N) would be able to eat something there too. Blue got a hoodie, which was once Papyrus', and put it on (Y/N). "This should keep you warm for now." She giggled at her 'silly' appearance. Blue chuckled at her cuteness and went to open the door.

"Come with me (Y/N)!" She then trotted over to Blue and out the door, slightly shivering at the cold air hitting her legs. Blue then shut and locked the door behind him and began walking to Muffet's. (Y/N) trotted close behind him, though she kept looking behind herself a lot. Blue noticed this and turned to see where she was looking, only to see that nothing was there. "What did you see (Y/N)?" The young foal looked up at him and shook her head lightly. "I (Thought) fought I saw somefing move really fast behind me." Blue nodded and had her now trotting next to him instead of behind him.

When they finally arrived at Muffet's Blue opened the door and (Y/N) walked through, but stopped and waited for Blue. Blue then came through and walked over to Papyrus and (Y/N) stayed close behind him. Blue seemed to love having her as his little companion. She followed him where ever he went and waited for him whenever he was behind her. She was just so adorable to him, even in the eyes of everyone at Muffet's, she was adorable.

Blue then nugged Papyrus' shoulder, only because he was asleep on the counter, and tried his best to wake him up without yelling. "Papyrus. Papyrus. Papyrus wake up!" Blue says, but his only response was a groggy Papyrus', "Nyeh?". "Papyrus. I have brought (Y/N) her to eat. We have nothing at home, so while I am gone getting the groceries, you must watch and feed (Y/N). Okay?" Papyrus just nods, not really knowing what Blue just said to him. Blue then gave (Y/N) a big hug and left.

(Y/N) then, after several minutes of waiting and getting hungry, decides to ask for something to eat. She pokes Papyrus' sleeping form and waits for him to move, or to respond. "Nyeh?" "Can I have somefing to eat pwease?" Papyrus then jolts up right and looks at her. She then falls backwards in surprise. "What are you doing here kid? Blue's gotta be worried sick about ya!" She then looks at him confused. "Bwue said you had to watch and feed me while he got food." Papyrus then nods. "Whatcha wantin' ta eat kiddo?" She gets up on her legs and shrugs. "(Your Pastry of Choice)." Papyrus then orders her a (Your Pastry of Choice).

She ate the delicious pastry and smiled brightly at Papyrus. He smirked back and knew he and his brother were going to have a lot of fun having her around.

(Word count: 1,601 )

(Sorry this took awhile to write! Hope you enjoyed!)