Crossover!

By now, everyone in Ponyville had heard the news: a mysterious wormhole had appeared in the center of town, a gateway to another reality, and that could only mean that a visitor from another world would soon be crossing over into Equestria.  The townsfolk reacted as they always did when something strange happened, by gathering outside of Twilight Sparkle's library and shouting angrily at nothing in particular until they got her attention.

"I know," said Twilight, as she exited her home.  "A wormhole opened up, and we'll probably be getting at least one visitor from another world, it will most likely be some sort of important hero or villain, and naturally we're all going to have to drop whatever we're doing and play along with whatever adventure or catastrophe results from their crossing over."

"Why can't these characters stay in their own dimensions!?" the mayor shouted.

"Seriously, can't we just build a brick house around the wormhole?" shouted Carrot Cake.  "Wait, is it still technically a house if we don't put any windows or doors on it?"

"Has anyone else noticed that this only started happening after Twilight moved to Ponyville?" shouted another resident.

"Please!" Twilight shouted, ignoring that last remark.  "I have a plan!  I'm going to spend the day researching all known occurrences of transdimensional portals in Equestria and the things that came out of them, then I'm going to compile a list of beings that are likely to come out of ours, and then I'll come up with a strategy to handle each possible scenario.  If we all work together, we can resolve this crossover event in a day or so and get back to our lives."  And so the townspeople departed with cautious optimism as Twilight retreated into her house to begin researching.

"What about this one?" Spike asked, placing a book on Twilight's desk.

"Hmm," she read the title aloud, "'Your Wormhole Has Ghosts In It'," she stopped reading the title and gave Spike a skeptical look.   "Spike, what have I told you?  Supernatural occurrences are just an old pony's tale, there are no such things as ghosts."

"But that's what you said when you guys were infected by the Poison Joke and-"

"No.  Such.  Thing."

"Fine, I'll keep looking," Spike sighed as he carried the book away.

"Let's see here," Twilight said, flipping through another history book, "Aha!  Thirty years ago, in Manehattan, a group of heroes calling themselves 'Transformers' crossed over into our world.  They were described as strange mechanical beings that transformed into strange mechanical things, they were really big, and demolished half of the city fighting their enemies.  Once they were victorious, they thanked the citizens of Manehattan for their aid, refused to divulge their insurance information, and abruptly crossed over back to their world, leaving hundreds of millions of bits worth of damage and hundreds injured in their wake to be paid for by the ponies who never actually had anything to do with the conflict.  Geez, let's hope it's not those guys."  She laughed nervously as she said this.

"Didn't the Princess issue an order for them to be dismantled on sight if they were ever seen again?" Spike asked.

"Yes, they were declared the first sentient natural disaster," Twilight replied.  "And a particularly ballsy toy company started manufacturing scale models of them to foals, got rich off of everpony else's misery."

"The nerve of some ponies," Spike said, as he continued to rummage through the shelves of books.

"Here's another one," Twilight said.  "A few years after that, a human known as the 'Bat Man' crossed over into Equestria, landing in Fillydelphia."

"Didn't that happen like three times?" Spike asked.

"Yes," Twilight replied, "and each time he was following a different adversary, all three of whom were trying to take revenge on the costumed vigilante for past offenses.  Fillydelphia was nearly destroyed on each occasion, but the conflict was enjoyable enough to be forgiven the first time around.  The second time, the battle was even more well-received, with Fillydelphians still saying to this day that it was the best fight they had ever seen.  The third battle, roughly eight years later, got mixed reviews from bystanders, many of whom said that they couldn't understand what the Bat Man's adversary was saying."

"I think that was the guy with the freaky headgear."

"In any case, we'll add that one to the list," Twilight said.  "This one was even stranger.  Ten years ago, Equestria had a crossover event with a human boy, though in his world he was the last of his kind.  He had a companion with him, a dog who was said to be able to alter his shape and mass at will.  They were following some sort of ice wizard who wound up freezing most of Trottingham's citizens before he was defeated.  Even though the ensuing frostbite resulted in numerous amputations, the two travelers forgave the ice wizard on the condition that he simply stop, as one bystander quoted 'acting like a poot'.  Most of the injured felt that justice was not served that day, very sad."

"Maybe the wizard was crazy," Spike suggested.  "Like, clinically insane."

"Then the world he came from should have had better mental health facilities, with better security.  The wizard was clearly a danger to himself and others.  So basically, what we could be dealing with so far are giant metal monsters with no insurance, a guy in a bat costume who seems to have a knack for angering crazy revolutionaries, and a pair of mental hospital orderlies."

"What about Dan?" Spike asked, his eyes drifting downward towards the floorboards.

"We're not going to talk about Dan," Twilight replied hastily.  "Honestly, I just wish these people would keep their problems to themselves.  We have enough to deal with without lumping in extra-dimensional villains and monsters."

"Equestria is nice place," Spike said.  "And most of the ponies here are very helpful.  Makes sense that others would want, or even feel encouraged, to come here for help."

"Wish I could hang a giant 'Do not disturb' sign outside of time and space," Twilight sighed.  "In any case, I think we've got enough data to work off of for now.  Let's start strategizing!"

...

"I don't know about this, Twilight," Applejack said, the following day.  There was a degree of uncertainty in her voice, surpassed only by the uncertainty she used said voice to vocalize.

"Trust me," Twilight said.  "I was up all night running simulation after simulation, I've done all the calculations, and the plan I've devised is the best possible way to ensure that this crossover event is as minor a headache as possible."

"Guess I'll take your word for it, then."

"Alright," Twilight said as the townspeople gathered around the wormhole, "is everyone on board with this plan?  The moment our inter-dimensional visitors step out of the wormhole and onto that pressure plate, the trebuchet will activate, launching them clear into buffalo territory."  Everyone cheered in agreement.

"Oh, I'm so nervous, I can't watch!" Pinkie Pie shouted as she buried her upper half in the ground.

"The wormhole is pulsating!" Twilight shouted, ignoring her friend's ostrich-like defense mechanism.  "This is it, we're about to make contact!"  Suddenly, Pinkie's upper half popped out of the wormhole.

"Oh!" Pinkie exclaimed as every jaw in Ponyville dropped at once.  "Silly me, this is where I left it!"  She retreated back into the hole and appeared to zip it closed from the inside, causing it to vanish.  "Ya know, I can't remember why I buried the thing in the first place," she said as she pulled herself up from out of the ground.

"What... was that?" A confused Twilight asked.

"What do you mean?  It was a wormhole, silly!"  She skipped away, humming to herself happily as Twilight's ears began to bleed.

"Told you to read the book," Spike said, handing the first book to her again.

"'Your Wormhole Has Ghosts In It'," she read again, "'Is What The Title Would Be If This Weren't a Set Up For Another Random Pinkie Pie Moment'."

"See?  The book had the explanation all along!" Spike said.  "I hope you learned a valuable lesson about not judging a book by its cover!"

"Spike, the book didn't explain jack shit," Twilight replied flatly.  "If anything, I'm more confused now than I was before."

"Well what else does the book say?"

"Well let's see," Twilight said, levitating the book and flipping through its pages.  "It's a biographical account of the past two days."

"That book's been on the shelf for at least a year..." Spike said, nervously.  "What do you suppose that means?"

"Nope," Twilight replied as she tossed the book onto the pressure plate and launched it into the horizon.