I had this very strange dream that I was watching one of the new (read: season 4) episodes of MLP, and it seemed like they wanted to foray into the horror genre for a short time.
It started out with that no one could find Granny Smith, and yet despite that it seemed as if she was still having mild physical influence on Ponyville. No one was quite sure what had happened. Well, until other ponies started randomly disappearing.
It seemed like the ponies were still physically present - they were in Ponyville - only they really couldn't interact well with the world around them, if they spoke they couldn't be heard, they couldn't be felt, so nopony knew that they were there, really, even if they were right next to a non-disappeared pony.
It was a Cutie Mark Crusaders-centric episode - well, them and Twilight Sparkle, anyway, who were taking refuge elsewhere in Ponyville, along with several others. But before anypony was really aware of what was happening, Applebloom went back to the farm to get something.
And four days later hadn't come back.
(Well, more accurately, she did return, but nopony could notice because of the weirdness of this invisibility thing.)
Twilight determined that whatever this was, it was contagious, and from then on made a point to protect herself from the other ponies - they were all taking refuge in the same space, after all. The camera left the refuge place temporarily (I can't remember why) and when it returned, Sweetie Belle had vanished, leaving a very despondent Scootaloo huddled on the floor. When Twilight asked what had happened, Scootaloo said she'd just turned a minute ago and Sweetie Belle was suddenly gone. Twilight decided it was time to figure out what the hell this was, so she risked going back to her house in order to pick up every book she had about magic in the hopes of figuring out how to defeat this phenomenon. Whilst in there, she noticed a book about "strange critters", including "sandglass spiders". Dropping all the other books she picked up and realized that this was the phenomenon sweeping Ponyville.
The sandglass spiders were little creatures engineered by the Germanes a while before (well, in my actual dream it was Nazis, but...) that were intended to be used as camouflage. Only problem was that they reproduced a lot and clung to ponies like metal to magnets and wouldn't go away, making them absolutely useless for combat as the Germanes had never figured out how to get them to go away. But as this was a book on these creatures, it had a solution.
Which I don't remember because I then woke up. But in a half-asleep state I decided that if this were an actual MLP ep, that while searching for the solution in her library, Twilight would find that the sandglass spiders are attacking her. Thinking quickly, she time-travels back to when Twilight is still refuging at the wherever-they-are place and quickly warns past-Twilight not to go looking for the book at her place, but she tells past-Twilight of the name of the book and says "use alternate means to obtain it" before vanishing.
Past-Twilight then thinks for a few minutes before looking at Scootaloo, who is still huddled next to where Sweetie Belle used to be (unbeknownst to her, both Sweetie Belle and Applebloom are with her), and realizing quickly that odds are Scootaloo is actually immune to the sandglass spiders, since she's been huddled next to a vanished Sweetie Belle for quite some time and hasn't shown any signs that the sandglass spiders are on her. So Twilight tasks Scootaloo with going to her house (in this dream apparently Scootaloo can actually use her wings to fly; this is important because the sandglass spiders can't fly, so Twilight thinks the best way to avoid them heading back to her house is to fly over them) and finding the book on the sandglass spiders and bringing it back. Scootaloo is understandably scared out of her mind, but manages to pull it off successfully, so Twilight can figure out the solution to the sandglass spiders and get everyone in Ponyville back to normal.
In my half-asleep state, this event was supposed to lead to Scootaloo getting her cutie mark. But that doesn't make a lot of sense, so I decided that instead she'd just be the hero of Ponyville and earn the respect of everyone, including Rainbow Dash.
... idk either