Morty knows he shouldn't be screwing around with multidimensional shit. It's dangerous, it's impractical, it's blah blah blah. But it's a potential key to unlimited energy, how does nobody see that? He's built a dimensional siphon (it kind of looks like a cardboard box with a funnel and a TI-84 taped to it, but it damn well works), keyed in the dimensional coordinates to a random plane, and by God he's going to use it.
He flips the switch and waits for the energy bar to fill up.
It does! It fills up very rapidly. Then it explodes, along with the box. There's rather more smoke than there should be, and once the smoke clears someone is standing there.
"Oh my," Morty says faintly.
He focuses his attention on Morty. His attention is... uncomfortably dense.
"Do you have a way to put me back? That would be new and different."
"This is the second time I've been suddenly transported to another universe. The first time it was a small cult looking to sacrifice me to their false god, so in that sense you represent an improvement. Well done."
He takes out his phone and dials an extension.
"Hello."
"What is it?" snaps a voice on the other end of the line.
"Mrs. Hartford, how good to-"
"What is it, you little slime?"
"Okay. I accidentally summoned someone from another-"
"You WHAT?"
He winces. "Yes. He says this 'is not the first time this has-'"
"I don't care, you little idiot! I'm sending the Headmistress over now."
"Well, I'm s-
There's a click from the other end.
"...Fine." He clicks the phone shut and actually looks angry enough to stop being petrified. He walks over to his window, muttering all the while. "Christ. Hartford is the biggest bitch in the universe, I swear to God."
He shifts the curtain to look out the window. "At least it's nice outside. Maybe I can have a picnic before they send me to space prison on the moon." He goes to open the window for Mrs. Carson.
And then Mark is there, holding the curtain shut and blocking access to the window.
"I am nastily allergic to direct sunlight," he says. "While it's possible that at least some of your problems would be solved if you opened the window and I caught fire, I don't recommend trying it."
She doesn't seem to be amused! However, after a moment of sizing up the situation, she relents and returns the rod to a guarding position. "I apologize. You are from another world; I shouldn't apply local assumptions of vampires to you. Speaking of which, I apologize for my student's behavior and assure you that it will be remedied as soon as possible."
"Until then... I would like you to explain to a psychic what abilities you have at your disposal and whether or not you intend to harm anyone here. If you are credibly not a threat, I will apologize again for my suspicion and you will be hosted here without incident. If you are something of a threat but do not appear immediately or intentionally harmful, you will be hosted in a higher security area and possibly allowed to wander under supervision." She refrains from listing the third option, in which the psychic tells her that he's pure evil and she destroys him. He probably picks up on it anyway.
"I can fly you over to Louis' tank in short order if you let me carry you. And protect you from the sun while you're there. If you'd rather not, we can take the tunnels. It's your choice; flight is quicker, but I will understand if you'd rather not hop into the arms of the woman most recently threatening your bodily integrity."
Inside a large tank is a horrible, horrible monster. It features many tentacles, but also an enormous quantity of other features that make so much less sense. Horns, wings, hooves, teeth- God, the teeth. Generally, it looks like something that shouldn't exist.
There's also a 30something man sitting in an armchair wearing a tweed suit and a Cthulhu beanie. He waves at them cheerily. "Good afternoon, Mrs. Carson. Pleasure to meet you, Miles. I do wish you could say the same, but I hope I can at least make your afternoon a bit better."