Alt. Universes or not

Okay, random thought.

There is a tag called Alt. Universe. But, all fanfictions aren't cannon, and thus must happen in an alternate universe.

OR....

The mirror pool clones of Pinkie come from our Fanfiction universes, so nothing is an alternate universe

So, the first answer suggests that Alt. Universe isn't necessary, and the other suggests Pinkie Pie is a killer that is forcing every pony into cannibalism
somewhere in the shows cannon. Have fun pondering the options.