In Universe 2-A-B, Celestia created a failsafe for when Nightmare Moon would return. This failsafe? To shrink all ponies to a micro size to hide them from invaders. Yeah, it's stupid, but she did make it in sorrow and panic.

Here, we see Nightmare Moon's return. She walks down the corridor in confusion. Where's the guards? Where is anypony? Unknown to the alicorn queen, there were two ponies nearby, as in under her hoof. They ran in a panic, hoping to outrun the massive hoof coming down upon them. One of them, Applepie, tripped, and her friend did nothing to help her.

Now, she will come out unharmed, as part of the failsafe spell was also make all ponies impervious to being crushed and digested. She'll find out soon enough, but a worse fate may befall her, getting discovered by Nightmare Moon.

Will Nightmare Moon discover them, Or will she just rule an "empty" Equestria?