"Oh, hello! First time at Milliways?"

"I must conclude the answer is yes," he says.

"Milliways is a transdimensional bar that likes hijacking random doors in myriad universes. The bar itself is sentient and female. She does very good drink recommendations, and can make things that don't exist in your universe of origin. In addition to beverages, she can also do...anything that's not alive, a weapon, or too large to fit on top of her."

"What an interesting set of qualifications."

"Weapons and alive things seem to be an ethical limitation, as far as I can tell. I'm not sure if she literally can't make things larger than herself or if it would just be unpleasant but either way I'm not asking her to."

"Hm," he says. "So, how transdimensional is the transdimensional bar? Clearly there's some selection for similarity going on since the bar appears to be approximately a bar and you appear to be approximately a human."

"There's some selection for Earths for some reason. And I am...debatably human."

"What are the sides of the debate?"

"Well, one side is that there's no actual evidence that mutants actually qualify as a separate species under any scientific definition. The other side is that the layperson public got their teeth into the idea and aren't going to let something like logic pry it away from them."

"That would be people, yes."

"They do persist in being people. Anyway. My name is Mark, if exchanging names is the sort of thing one does in a transdimensional bar."

"Among other things, yes. I'm Emily. It's nice to meet you."

"It's certainly the most interesting thing that has happened to me this week. What's your universe like?"

"Late twentieth century Earth, mostly standard except with mutants and some boosted technological development from the fact that I've been coming here for years and know people who can reverse-engineer gadgets I bring home."

"That must be convenient. 2999 for me, and we have an Earth but I haven't been there in a while."

"Oh, I met a guy in here a few weeks back who was from 2999 and a not-Earth planet. Maybe you're from the same universe."

"Yeah? Did he mention any identifying features of the universe in question?"

"A planet called Barrayar with some unfortunate habits regarding physical differences, a couple of other planets called...Escobar and Tau Ceti, the Earth's atmosphere hasn't been lost to pollution, Oxford still exists..."

"...What?"

"It's just... an interesting coincidence that Barrayar was the first planet you mentioned. I have family there."

"Well, apparently it practices infanticide. And has opinions on people called mutants, that's pretty relevant to me. Plus the guy I met was from there, that's...actually how I learned about the other stuff, was that I mentioned I was a mutant and he reacted."

"How badly?"