Operation: Incentive - Invader Zim fanfic (ZADF)

Pain.

The pain almost made Dib black out. It felt like every nerve in his body was on fire, and it was pure agony. He clamped his hand over his mouth as a reflex, but when his stomach started churning, he knew he couldn't hold it in much longer. He raised his hand.
"Mrs. Bitters, can I PLEASE go to the toilet?"
She looked at him haughtily, and replied, "Fine, but don't expect to go again this year."
As he ran out of the room, one hand on his mouth and the other on his kidney, he faintly registered that no one had realized he was unwell. No one, that is, apart from Zim. He didn't question this at the time, though, as the moment he got to the toilet, everything spewed out of his mouth. He was dizzy, disoriented, and he stumbled around the stall like a drunk man. His head throbbed. His heart thudded against his chest. This was torture, let it end! His knees buckled and he hit the ground hard, with no strength left in his legs. He willed himself to move towards the toilet, and he crawled towards it, before his arms lost their power too. His coat slipped off his numb shoulders. He sat prone on the floor next to the look, and as the next barrage of vomit came through his mouth, he vaguely noted weird shapes in the toilet. Gosh, was  that an intestine? He thought he must be hallucinating: there was no other explanation. That must be it. He was going into shock from whatever this pain was, and he was having issues with trying to think straight. And sit straight. And breathe right. As his world faded into darkness, Dib was grateful for the sweet release of unconsciousness.

Dib woke up. He didn't know how long he had been on the floor, but it felt like an eternity. He wondered, quite absentmindedly, why he felt so sick. The suffering he had felt had mostly faded by now, but his head ached, and his vision was a little hazy.

He tried to recall the events between this morning and getting sick. Getting sick...sick... Was he truly hallucinating earlier? He stood up carefully, and stumbled over to the toilet. He took a peek... and felt his stomach drop. He wasn't hallucinating. In the toilet lay a bloody intestine, coiling up in delicate circles. Below it was more blood, and lumps of flesh that Dib didn't even want to further examine... Was it his? It had to be... Didn't it? He'd never heard of a sickness where you literally spew your guts out! But, he corrected himself, this couldn't be a sickness... Or if it was, it certainly wasn't human. And how was he functioning without his intestine?

No, he told himself. This was Zim. He raised his hand to his neck, and felt the welt he'd felt earlier. It felt larger, as if it had puffed up during his brief illness. That just confirmed Dib's view.  It had to be Zim. He flushed the toilet gingerly, pulled on his coat and exited the stall.

Dib walked up to the mirror, but didn't look in yet. He surveyed his surroundings, and luckily there was no one else in the toilets. He was safe.
He turned to his reflection.

The welt had turned a sickening shade of green, and had swelled to twice its previous side, but that didn't worry Dib.

No, what worried him was that one of his eyes was turning blue.