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.
In-person Peter is even more attractive than the illusory version, it turns out.
Louis sniffs. "It was Marvin Gaye, you philistine."
Peter rolls his eyes and holds out the longer of his right hands. "Peter. Nice to meet you."
Mark shakes Peter's hand. "Mark. Likewise. I might mind Louis's idea of tact more if he wasn't so fucking adorable about it."
Louis, now sporting a stylish fishbowl hat, nods sadly. "Captivity disagrees with me."
"So, you're a vampire from a parallel universe. Are there many vampires? Do you, you know..." He mimes a "grr, argh" sort of gesture.
"I'm actually from two parallel universes," he says. "I picked up vampirism in between home and here. That universe is absolutely crawling with 'em, and they are mostly bloodthirsty assholes. I won't claim I don't thirst for blood, but I'm not inclined to kill anyone over it."
"I wouldn't call that the least plausible part of you that's spiked," notes Louis innocently.
Peter glares, but refuses to comment.
"Were you purpose-made to murder unsuspecting humans, if that isn't a rude question?" (Having sort of been purpose-made to murder unsuspecting humans himself, Mark feels that he gets to ask it if anybody does.)
"Very few of us were purpose-made to do anything. Mutants are naturally occurring. Louis is of the opinion that I'm like this because my thirteen-year-old-self thought it would look cool, which is believable. Also, he was a bit more ambivalent on the subject of murder. I mean, killing people is all well and good, but if there's no good reason behind it it just seems a bit pointless, you know? Sort of declassé."
"In defense of your thirteen-year-old self, it does look cool."
The fact that vampires can't blush is extremely useful. So is the fact that Mark has a tendency to default to expressionlessness. See how calm and collected and not at all awkward he looks!
Peter sighs. "I should, actually, probably show you around. If for no other reason than to get us out of Louis' domain so he can stop harassing you."
"Suits me," he says, still outwardly unruffled. "Is whatever that other person did to prevent me catching fire in sunlight still active?"
First, Mark is shown around Hawthorne. Peter shows him various safety precautions, including an extremely mad-scientific fire extinguishing system and several rooms designed for flagrantly explosive mutants. "Since you don't exude nerve gas or anything, I don't think you'll need one of the special rooms. So your room is probably going to be more of a standard dorm than anything else, just fit with blackout curtains."