Gaster AU x Reader ONESHOTS

Dadster Gaster x Young! Child! Reader

Your parents were running from Undyne in the water falls, your mother was holding a small baby in a (f/c) blanket while your dad tried to block the spears. "(D/n)! We can't run like this forever!" You mom cried in despair, your dad looked around until he noticed a skeleton near a iron door. "Let's give (y/n) to that man." "B-but-!" "(M/n)! (Y/n) is safer with him than anyone else." Your mother nodded as she handed you to your father and watched him run over to this skeleton. "Sir! Sir!" Your father called, you started to cry as your father reached the monster.

"Please take our (daughter/son)! A fish lady is trying to kill us, (y/n) is far to young to die. Please sir! We just want (him/her) safe!" Your father begged, the skeleton took you from his arms, you opened your (e/c) eyes and looked at this skeleton. You reached for him as you laughed and giggled. "I will." "Oh thank you!" Just like that, your dad left as this skeleton opened the iron door and took you inside. '(Y/n) is a lovely name for this child...' the skeleton thought to himself as you slept in his arms.

- 6 years later -

"Daddy!" You ran to Gaster in a (f/c) shirt and jeans with your socks and hair a mess. "Yes, (y/n)?" Gaster asked, you were snickering as you thought of a good joke. "You're my dad right?" "Yes." "Aaand your name is Gaster, right?" "That is correct." "So," you climbed onto Gaster's lap and prepared the jazz hands. "Does that make you my... DADster?!" You asked with the jazz hands, Gaster had a pink on his face before he placed his pencil down and hugged you. "Your first pun! I'm so proud!"

You hugged Gaster back as you laughed at your own pun. Soon you watched him work before you picked up a pencil and post it note and started to copy him. "What are you doing, (y/n)?" Gaster asked as you copied his writing. You gave Gaster the paper as he read it.

✋ ☹⚐✞☜ ✡⚐🕆 👎✌👎👎✡✏
(I love you Daddy!)

Gaster smiled and ruffled your hair as you giggled, "I love you too, (y/n)!" Gaster happily said as you giggled. "Now, will you please get dressed? It's almost noon." "Aaand if I don't?" Gaster smiled and placed his pencil down, you kinda reminded him of Sans when he was a baby bones. "Then," Gaster started to tickle your sides as you giggled, "you'll face the wreath of the Dadster!" You kept giggling before Gaster used his magic hands to bring over your clothes and brush. "Now, get dressed." Gaster ordered, you nodded and took the items from the magic hand before going to your room.

Gaster smiled and returned to his work as he enjoyed being a dad again. Then, he started to think. You were turning seven in three days. Should you know the truth? Gaster sighed as you came back in your usual clothes. "(Y/n), come here." You walked over as Gaster lifted you to his lap. "There is something you should know." You nodded before Gaster started to story of how you were given to him. In the end, Gaster was in tears. "Daddy... I still love you..." Gaster was shocked as you hugged him, Gaster sighed in almost relief as he hugged you back.

*dies of cuteness*