"Get ready!" He held the syringe up to the Toad.

"Are you SURE this isn't going to hurt?"

"No more than a usual shot, my friend!"

"You probably should've asked if I wanted to back out, first."

"Too late for that." The scientist said, inserting the small needle into the Toad's arm. "Let me know if you feel sick."

Two days later:

The scientist was busy unpacking their things for the day. He had been trying to find a cure for a rare disease, but all of them had led to failure. There was a bang on the door, and he opened it.

The Toad from earlier was back but had a small group of dark red Mushrooms growing out of a blood red scar. His eyes looked...life-less. He dragged himself into the room, towards the scientist.

He backed the doctor into the far wall.

Nobody has heard of the scientist since that incident. The Mushrooms started spreading. Eventually, they were named "Shroomitz". A cure was in progress, but every time somebody tried to make it, they became one of the "Shroomed".

It seemed like a cure was never possible, and the world would fall apart thanks to the Shroomitz...