Undertale x Child!Reader Scenarios

Babysitter, Part 1

Quick Author's Note: Mettaton will be in his normal, boxlike form for this oneshot. (More energy-efficient according to him, remember?)

You were just a baby monster when your parents "donated" you to be part of the research of the royal scientist. As with all of Alphys' experiments, the injection of raw Determination warped your body in horrifying ways. Because of your age, the experiment nearly killed you.

Alphys took more sympathy on you than any of her other creations, and that, coupled with the realization that your cruel parents would never take you back like this, convinced her to raise you as her own. She named you (Y/N).

That was just a couple months ago. A LOT has happened since then. The barrier has been broken, and the monsters have moved aboveground.

Alphys took you with her to her new home and set up a new laboratory as quickly as possible. Your unstable physiology meant that you were high-maintenance and needed frequent care in the form of examinations and injections.

One day, Mettaton, one of Alphys' other creations, came over in response to an urgent call from the scientist.

//Mettaton P.O.V.//

"You needed me, Doctor?"

Alphys looked relieved when I entered her home. "Oh thank heavens you're here, Mettaton! I need to go on a grocery-and-tools run and I need someone to watch (Y/N).

(Y/N)? Who... oh yes, one of her failed experiment things. I had seen the little thing around whenever I visited, and I was not a fan of it.

I gave a disgruntled beep. "I'm not babysitting that little abomination."

"B-but this is an urgent errand trip!"

"(Y/N) is so... oozy, though. Have you seen the sludge that comes from their (eyes and/or mouth, your choice!)?"

"Every day, Mettaton." Alphys was starting to get cross. "I kn-know you don't like them, but (Y/N) i-is really high-maintenance, a-and I need you to take care of them! Come on, j-just once? For me?"

I eventually agreed, but only after a long, dramatic sigh. The doctor was ecstatic. She handed me a schedule for (Y/N)'s care routine, then left.

I wheeled around the house, looking for the monstrous (no pun intended) infant. It didn't take long for me to find them rolling around on the dining room floor. The sludge that leaked from their face was everywhere.

Groaning, I put the schedule down on the table and got to work cleaning up the mess. But I gave up halfway through when I realized there was just going to be more sludge being constantly produced and oozing everywhere.

I glanced at the clock in the kitchen, then at the schedule.

11:45 a.m.— Lunch for (Y/N). They will eat pretty much anything, but keep them away from sugary stuff unless you want to hear unholy hyper screeching for the next five hours.

How fun.

I fixed them (Favorite Food) and placed it on the dining table. I then put (Y/N) in a high chair in front of the meal.

The young monster's mouth stretched to a horrific size, and they consumed their lunch in a single bite. They looked at me with what I assumed to be a happy expression. It was hard to tell with that crooked face.

(Y/N) appeared to be satisfied for now, so I set them back down on the floor. They stared up at me and vibrated for a few seconds before licking the stalk connecting my wheel to my body.

Apparently, just because I fed them once, they love me. This thing was honestly acting more like a pet than an actual monster.

The next few hours passed by without much excitement. I gave (Y/N) injections from helpfully labelled, already-filled syringes according to Alphys' directions in the schedule. At one point I found a gray puddle on the kitchen floor that definitely wasn't there before and looked to be corroding the tiles. I would have to ask about that later.

I soon got a call on the home phone. I picked it up, and it was Papyrus. I explained that Alphys wasn't home, but he didn't seem bothered by that and asked if I wanted to come over to watch movies with him and Sans.

I looked at (Y/N) lying on the couch, still oozing, and got an idea.

"I'll be there."