During the zap-apple harvest, Applejack almost finished the job, so she goes to the last tree to conclude that and gaining more reserves for the Zap Apple Jam. Everything looked normal..... If wasn't for a very unusual factor.

Leaving the harvest for a moment to retrieve her hat, she found a grotesque, strange reddish rainbow patterned zap-apple in front of her, outright out of any natural process. She tried to pick it up due to her curiosity. Applejack couldn't know that, but that act was enough to mark the end of normality, and what happened next was a series of strange, chilling events that looked like horrible coincidences.

Such events were too nightmarish to be real. The only thing it need to become reality was one catalyst:

Her body.

Three things:

1) The Sex tag was present because I may have the need to describe some organic or anatomic details. That is what I think.

2)The description is vague and may seem pretentious because I don't want spoil anything.

3)No Zap Swarm Disease Whatever is involved.