Like this guy!

He seems quite confused by what can be found the other side of the door he's just gone through.

Doesn't seem to have a shirt on, does he.

Well, it looks like someone improvised a dormitory inside a bar and there are three boys, identical ones at that, hang around.

One is just wearing... hard to tell if those are shorts or boxers.

Another is wearing something that provides much more covering.

And the third is wearing pajama pants.

The newcomer is wearing… pretty much the same as that last one.

"Umwhat."

"Hey! Fresh meat, finally!"

"Don't be mean, Trevor. Hello, newcomer. This is a interdimensional hub that randomly possesses doors, bringing patrons from all over the multiverse, usually it presents itself like a bar. Today it decided to throw a pajama party and has been catching people in their sleepwear. I am Felix, these are my brothers Trevor and Fenris. We are from United States, Earth, 2015."

"Earth, United States, um, 2016," he says. "Interdimensional hub bar that uses doors, right."

"Oh, another Earth. There are lot of those, it turns out, often with different types of magic, like ours."

He waves at Fenris.

Fenris levitates several inches from the ground.

"Nope," he says, a bit higher pitched than before. "Nope, pretty sure my world– nope."

"Sorry? Is this too much at once?"

"I am fffine," he says. "Just adjusting – keep going though."

"Well, there are various kinds of magic, in our world it manifests as various powers and people use them to become super-heroes or super-villains. We are super-heroes."

"I would hope so," he says, then looks at the doorway that he's still standing in. "Uh, how many people get these powers?"

He'll come in from the doorway a little. Since it hijacks doors, wouldn't want to be split in half or something horrible.

"The number is just shy of two million today."

"You know, we don't bite," Trevor observes, "unless you ask nicely."

He raises an eyebrow. "How many people do you have on your planet in total, then?"

"Seven billion. 21th century Earths tend to be pretty standard on that regard, apparently. There is some higher concentration of people with powers on the United States. Powers are caused by something called the Ternion Agent, that is contagious - you are safe in Milliways - and it spread from there."

"Are they a bad thing, do they have detrimental side effects?"

"The powers are not, but about a third of whoever catches the Ternion Agent dies and a third develops powers. As I said you are safe, Milliways filters this kind of stuff and people with powers are not contagious."

He nods. "Mutually exclusive thirds or can they sometimes overlap, like, someone gets powers and dies a day later?"

"Technically, impossible to actually tell, the Ternion Argent induces a comatose state and if you don't wake up there is no way of knowing."

"Uh, on the plus side, the spread is thoroughly contained and nowadays."

"So is it a half of all that wake up or is it a third of all that wake up that get powers? And uh yeah. Ew."