Chara, you decided, was a cute kid. They however were not cute enough to keep pulling this kind of shit.
You had woken up in your office/bedroom in the Labs after passing out from another all-nighter to find the kid and their "goat-bro" sneaking in. This wouldn't be so much of an issue if you had been babysitting them and left them temporarily with one of the scientist to take a nap. You had not been the one watching them today however. In fact, you had not been bringing them to the Labs since the construction of the CORE started do to the heavy machinery that now littered the floor as you manufactured parts on the grand scale.
They were not supposed to be here until it was safe enough again. It was barely safe enough for you and your staff most days, you couldn't afford them being underfoot. "Ehem." You made a clear throat clearing noise startling them.
"Uncle Gaster!" "Dr. Gaster!" You were starting to wish Chara called you Uncle too now that they were calling Toriel and Asgore Mom and Dad.
"Just what do you two think you are doing here? You're a long way from Home."
"We hadn't seen the Lab in a while. We wanted to see what you were working on."
"Dad said it was important but he never would explain anything." Chara complained.
"That would be because you father only ever skims my detailed written reports. If that. He trusts my judgment will not blow us all up so he can focus on other areas that need more supervision like the moving of the Capital. As for what I am doing here, I am building something that is rather dangerous for the two of you to just run about and in between." You give them both you best disapproving look.
They both look rather embarrassed. "Can you not tell our parents we snuck out here at least?"
"Oh no. I fully intend on telling them that you managed to cross half the Underground unsupervised and then snuck in here. I will also be having a word with my staff about how you managed to get all the way to the bottom level on your own without anyone stopping you."
This was the part that concerned you the most. While, yes the trip to the Lab was not exactly the safest trip ever, that was something you could see them doing easily enough. What you could not see was them finding the service elevator and riding it down without help. The majority of the Labs were inaccessible unless you took it and you had to even know about it to use it in the first place.
You had the designed the Labs like this for safety reasons. It keep the majority of monsters from walking in on dangerous experiments or tripping over dangerous equipment. The fact that this was how the True Lab in the Game had been designed had actually slipped your mind until you looked at the final map of the rooms of the bottom floor. It had just made sense at the time and it still did. You had reached the point where the Game was factoring less and less into what you did anyways. A good thing too, since with how many decades had passed now, it was getting harder and harder to remember the fine details.
The kids eventually admitted that they had help sneaking in, Dr. Pialtal (the armless yellow orange reptile monster) had found them on the upper level and brought them down to your door. He had been planning on waking you so you could take them home and tell their parents when they made a break for it when the elevator doors opened. As far as they knew, he was still looking for them.
You sigh and pick them up, aided slightly with your blue magic. The two of them laugh slightly as you hover them in the air down the hall behind you to find Pialtal. You do find him eventually, bent over to look under a piece of equipment. "Ehem. I believe you are looking for these?"
The two kids laugh louder as he jumps and spins to face you. "Dr. Gaster! I am so sorry! They just ran off when the doors opened. I was-"
"Save it. I am leaving early to take these two brats home. I was just letting you know I found them so you could get back to work."
"Oh! Uh, right away!" He turned tail and ran.
You sigh and turn to the kids. "Alright. Who's up for taking a shortcut home?"
"A shortcut?"
You wait a moment for them to both have their eyes closed and teleport to the front of the house in Home. When they open their eyes you're there. No reason for them to see into the Void. "A shortcut."
"Wha-"
"That was so cool!" Asriel's shout immediately summoned his mother from the house.
"ASRIEL AND CHARA DREEMURR! WHERE HAVE YOU BEEN?" You drop them to the ground but don't release them from your blue magic, pinning them. Toriel comes storming from the house and connects the dots when she sees you there. "Hotland?"
"They made it all the way down to my office." The two of them shift nervously from one foot to the other.
"How?"
"They ran into one of my staff right outside the Labs and he tried to bring them down to me. They bolted from his care when the elevator opened. Now if there isn't anything else, I think I am going to go to bed."
Toriel bid you goodnight, though that meant little down here, and you teleported back to the Lab. You were greeted by an explosion. You groaned and hurried toward the problem. And Asgore and Toriel wondered why you never got any sleep.
Notes:
A little bit of fluff to start the week. Friday's update might go up as early as Thursday night this week. I am going to a RTX in Austin this weekend and I am concerned that if I wait until Friday to post Friday's chapter It won't get up until Sunday. I would rather get it up a day early then two late. Next chapter, timeskipping all over the place. And not always in the way you would expect.