"Hey, is there somepony missing today?"
Twilight grunted as she looked about the room. All five of her friends were there, plus Spike. And Starlight. In fact, even Sunset Shimmer had come today.
And yet...
"Yeah, where's Twilight?" Rainbow Dash replied, "She was right there like, twenty seconds ago."
A low murmur began to emanate from the collective mouths of the ponies, all whispering about Twilight's abrupt disappearance.
"I'm right here," Twilight began, stomping her hoof down in mild irritation, "Can't you see?"
The mares (and dragon) continued to forego the presence of their chatter.
"Hello?" Twilight called again, waving a hoof in her friend's faces.
She passed right through them.
"Wat."
Just then, Spike coughed up a letter from Princess Celestia. He nervously grabbed it from the floor, unsure of what to do without Twilight's guidance.
"Just read it already," Applejack deadpanned, "Maybe it's got somethin' to do with Twi goin' missin'."
Spike nodded, and read the rather short letter.
Dear Twilight, please ignore the fact that you're currently in an altered state of reality. I accidentally stepped on a banana peel in the Canterlot Library of High Magicks, and might've... cast a spell in alarm.
There is no need to be alarmed, as the spell will wear off within five moons. For now, you are currently residing in a "bubble universe" created by the spell, and as such, there is no way for you to physically interact with the environment around you.
"I... I don't understand," Rarity began after Spike finished reading, "if the letter is meant for Twilight, then how would the message possibly get to her?"
Spike flipped the parchment around to the other side to find more text.
(P.S. - The moment I realized what I had done, I immediately cast a counterspell, but it was already too late. Luckily, the spell partially worked, and you can still have a one-way interaction with everything else. Namely, you can't do anything, but everything can still happen to you.
Also, WHO THE BUCK LEFT A BANANA PEEL IN THE LIBRARY?!
"Well then."