That Kid From Upstairs [Invader Zim x Reader]

Prologue

The young Membrane narrowed his eyes behind his thick glassed spectacles as his newest classmate marched (and he cannot stress it enough, marched, like a soldier,) into the room and sat in his designated seat. It didn't take long for his glare to be returned, as the green skinned "child" quietly snarled at him from across the room. Their teacher had yet to arrive.

...in fact, she was late.

An air of, a lot of things, was let loose in the otherwise silent room. Relief, mild euphoria, a whole lot of anxiety- and let us not forget the straigh up palpable hateful tension floating between the two boys in the front row.

Seeing this as a clear opportunity, Dib thought about springing from his seat and starting a rant about aliens (a very specific alien) first thing in the morning. He did love to do that. It was a shame his audience was brain-dead. He almost thought better of it in the spirit of Monday, but his inner paranormal investigator could not wait.

Nor could his nerves, as he vaguely saw Zim roll his eyes at him, already knowing what was about to happen.

His small hands barely connected with his already abused desk when the classroom door shot open, bouncing off of the wall with a loud slam. The already heavy silence seemed to deepen even further.

A tall person stood in the doorway, their forearm raised to stop the door from taking it's revenge on their face after springing back. Their right foot hovered an inch or two above the ground, likely after just kicking the poor door open. Dib could make out an obvious splinter in the wood. The person also seemed to take notice, as they quietly hissed at the door's metaphorical pain (and what punishment they would probably get for it).

The children blinked a few times in confusion. This obviously wasn't their teacher- a substitute maybe? What happened to the old woman? Not that they were worried.

The person stepped into the room, silencing any thoughts running through the children's heads. If they were capable of thinking that is.

"Good morning, dearest Pipsqueaks! Y'all are Elizabeth's seventh graders, yes?"

They sounded young. Did they just call Ms. Bitters by her first name? They didn't even know she had a first name-

"Are you from Upstairs?"

Dib spoke up suddenly. The tall student's attention was now on him, making him straighten up in his seat. They gave him a grin of approval as they nodded to the younger children.

"Well, yes! I'm here visiting from 11/A. I will be staying with you guys for a few weeks- maybe months. Depends on how long the old hag is willing to put up with me."

A few kids giggled from further back, seemingly feeding the newcomer's confidence.

"Right, I suppose you deserve an explanation. I have gotten into a... Well fight is a strong word- a disagreement, with a few of our schoolmates from 10/B. During which, they may have sustained a few...health complications, that...excuse them, of their duties for a few days."

Pretty much nobody liked the sound of that.

"The head honchos refused to suspend me because I'm the only one keeping my class's average above a failing grade, so they sent me here instead as punishment."

They rambled in an uplifted tone as they paced up and down the front of the room. They stopped at Dib's desk, briefly leaning on it to ruffle his hair. He swatted their hand away with an annoyed whine.

"Heh. Anyhow, there's a few things you should know."

They raised their pointer up with importance.

"Any grade I receive here will count towards my own class' statistics, not yours. I will not bother you, and I trust you will not bother me. You don't need to know my name. Don't bother telling me yours, I will forget them."

As they turned to walk across the room again, they caught sight of someone. Dib quickly realised who it was.

They dropped their hand to their side as they blinked at Zim, who was watching them with little stars in his glassy eyes.

"...ya good, big man-?"

Zim seemed to snap out of his starstruck daze and violently cleared his throat.

"YES! Zim is quite 'good'!"

"...Zim is not familiar with the concept of 'inside voice', apparently-"

"That's because he's an alien!"

Dib shouted with obvious frustration. The green boy took a deep breath and prepared to scream something (most likely "LIES!"), when the classroom door slammed open once again, now with only the usual ferocity.

All eyes snapped to the doorway.

Deep silence.

Until-

"Bethy!"

The unruly upperclassman cheered as Ms. Bitters scrunched her nose up in absolute disgust.

"You..."

She spat, as if the word was rotten to the taste.

"Oh how I missed you, remember how well we got along back when you had my class in 7th-"

"We did not."

The student scoffed light-heartedly.

"Why are you so negative?"

"I knew they were sending someone down, but had I known it was you, I wouldn't have come in today."

She hissed with obvious resentment. The person seemed to grin even harder.

"How unfortunate."

"Sit."

They bit back a giggle as they raised their hands in surrender, turning to walk to the back of the class. They paused when Dib grasped their sleeve.

"What are you doing?"

He asked, completely bewildered by their behaviour.

"What I've done throughout my school years thus far.

Whatever I want."