Or something like that. I'm not sure, the problem with wanting to give the stories mentioned here beginnings is that I don't know where all of them begin. Though an argument can be made for different beginning points for the ones I've done already (mermaid, band), anyway... Here:
The revelation - which from one perspective wasn't much of a revelation at all but from another placed all that had happened was happening, and would happen into it's proper context without which it could not be understood - happened on a couch. Before the revelation two young women were sleeping on it, for it belonged to one and the other was her girlfriend, they'd fallen asleep watching a science fiction marathon together and the TV had turned itself off. This was not because the TV had some special setting to turn it off when no one was watching but because a seagull had flapped it's wings unnecessarily a few days earlier and this whimsical wing flapping had caused disruptions in weather patterns up and down the east coast. Many miles west a wind thunderstorm caused a cracked branch to buckle leading it to lean on a precariously placed power line. Power to the line was quickly cut. Rerouted power heated other lines causing them to collide with the close branches of bordering trees and a cascading failure cut power to the couch's house for 1.25436 seconds. When power returned the TV remained off.
Of the young women, both were high school seniors but one had remained earthbound while the other had traveled extensively through space and much less extensively through time (she did not own the couch.) The young woman who did own the couch began to awake and, as she did, called the one laying in front of her, whom she had an arm around, by the wrong name. Which was the right name.
That is when the revelation took place.
Rachel, for that is what the owner of the couch was called, was warmly snuggled between her companion and the back of the couch and as she began to awaken, but her senses had not yet fully returned to her, spoke to her companion. What she intended to say she would soon forget, and it would never be remembered again and therefore cannot be seen to have any importance either to the universe at large or her story in particular. What she did say, sleepily, was, "Laurence."
To which the other young woman replied, "What?" in a groggy kind of way.
Now more awake and full of the strangest sense of mixed wrongness and rightness, Rachel asked, "Laurence?"
To which the other young woman replied, "I said, 'What,'" in a way that was still fairly groggy way.
Rachel bolted upright. Or as close to upright as she could manage which was more of a forty-five degree angle supported by her right arm on the couch. The couch, not accustomed to such sudden movements, shook and shuddered. The young woman who was not Rachel was now as awake as Rachel, which is to say fully awake, and startled by Rachel's action. She rolled her legs off the couch and from the resulting kneeling position stood. "Something wrong?" she asked, leaving any sign of a verb out of the sentence for she spoke that way.
Rachel also stood and said, "I called you the wrong name."
The not-Rachel woman shrugged, "These things happen."
"You responded to it."
"I was tired, I'd probably have responded to 'Mao'."
'Nononono," Rachel said, slurring her repetitions into a single word the way a painter might mix multiple colors to get the right tint, "You responded to it because it was your name. You responded like you'd been answering to it your whole life."
"I don't even remember what name it was."
"How could you not tell me?"
"How do you even think I know what you're talking about? What name was it if not Kiri?" the not-Rachel young woman who did indeed go by 'Kiri' asked.
"Laurence. Don't play games with me."
"Oh," Kiri said. "That name."
"Why didn't you tell me it was you?"
"Well I wasn't sure it would be a good thing to do."
"What part of, 'Hi. I'm me. I'm alive. I'm back. I'm hot,' isn't good?"
"Well... when you put it that way..." there was an awkward silence until Kiri said, "Our attempt at a relationship before failed because I was male and I wasn't sure that opening up with, 'Hey, I used to be male,' would work out all that well."
"How about, 'Hi, we already love each other and the only problem before was my body which is different now,'... speaking of which... how?"
Kiri sat on the couch, which had been neglected for the entire conversation thus far. Rachel sat next to her. "I am sure that there is a perfectly rational scientific explanation," Kiri began, "but since I don't know what that is I'm going to go with magic."
"Could you be more specific?"
"Look, one moment I was inside of a black hole and the next I was back on earth in a female body. Mercifully clothed."
"You were inside of a black hole?"
"These things happen."
"Any other revelations you'd care to hit me with."
"I'm older than you now."
"That's not possible."
Kiri raised an eyebrow, "Of everything that I said that's where you draw the line?"
"I was born before you, I'm older."
"Yeah, well now I am."
"That thing with the black hole won't happen for another couple of years, when I ended up back on earth I ended up in the past. This being the past. See, doesn't it look like the past to you."
"It feels kind of present to me."
"I would have gone with future, supercomputers that people carry around in their pockets connected to a vast global network that contains the whole of human knowledge and is so taken for granted that people use it to find pictures of kittens with misspelled captions. Very future-like."
"So you went back in time."
"And thus have lived longer than you."
"And therefore claim to be older."
"I am older. I'm about as much older now as I was younger then. We've swapped positions."
"Even if I conceede that you're older-"
"Which you should."
"- I still feel like I haven't been given an adequate explanation of things."
"Well you see, once upon a time I met a girl."
"That being me."
"Yes, and we fell in love."
"Which was awkward as all hell."
"Not to mention that one of your friends though you were intentionally setting me up for a fall."
"She's not my friend anymore."
"I noticed. Good call. But I figured chronological order works best for this stuff."
"Then go on."
The couch said nothing.
"Ok... so, um... remember how our last attempt at a relationship failed?"
"I remember that closing my eyes and pretending you were a girl only worked for about two and a half seconds."
"Ah, but what a two and a half seconds it was."
"It was a good kiss... while it lasted."
The couch still had no comment.
Rachel ended the silence, "And after that we decided not to try anymore because trying and failing was worse than not trying."
"And then you got distant. And then you disappeared."
"Yeah, well, being around you all the time with the failure of our various attempts at relationship in my mind was worse than not being around you so I... uh..."
"Built a space ship and left earth."
[rest of story begins with flashback to that point.]