For a long time, Flash Sentry of Equestria had a colthood crush on Princess Celestia's personal protégé. She was hot-tempered, and not all that humble, but young Flash sensed something that she desperately needed; a friend. He had always wanted to be that friend, but alas, she disappeared one day, and was never heard of since. Until Celestia's other student became princess. He was delighted, and ashamed to hear what Sunset had done, and for a time after Princess Twilight returned, he had went out with her, feeling some other worldly connection. That connection, however didn't last, and his heart still felt tied to his colthood crush.
He decided to talk about it with Twilight, being honest and telling her about the mare he truly loved. Moved by his words, and also feeling a loss of connection with this version of her love, decided to write to Sunset Shimmer with a great idea.
At Canterlot High, Flash Sentry only had one person on his mind; Twilight Sparkle.
He couldn't deny it, he was in love with a pony from another dimension. He rarely talked about his feelings, and when he did, it was either to his closest friends, since they understood the mad concept, or to Twilight's friends.
One day at a band-jam in the music room, Sunset's backpack started to hum, and vibrate. The band stopped as the old student to the Sun Princess opened her bag, and her book, and began to read what the Princess of Friendship wrote.
"Dear, Sunset Shimmer,
Hi, how is everypo-everybody? Good, I hope, anyway, I have an idea.
I've been seeing the Flash Sentry of our world, and we aren't happy, and here's why; He's in love with you, Sunset. I know it sounds crazy, but he's been an admirer of yours since you were Celestia's student. I think you two would get along well, and if I can be honest.....I miss my Flash.
So, here's what I'm thinking. Tomorrow, or whatever time it is....anyway, you let my Flash know about this, and then write me back. I'll open the portal, and send your Flash though the portal. We'll do a switch so the dimensions will stay in balance.
I hope this is okay with you, and you'll have to help him adjust to waking on two legs, and eating.....anyway, just let me know what you think, and when you're ready.
Your faithful friend,
Sunset thought about this, and discussed it with the other Rainbooms, and they all agreed that Flash shouldn't be miserable anymore. So they set off to find the blue-haired guitarist, and presented the idea to him.
He practically leaped at the chance to be with Twilight. The girls had to calm him down, and Sunset had to make him aware of the changes, and what he'd be getting into. She did what she could to describe the world she knew, but the more he heard the more he liked it. So what if his counterpart was a guard? That didn't mean he had to be. Maybe his"cutie mark" could just be him being a songwriter with lyrics that shocked people, but also made them feel safe.
In any case, he was certain, and that afternoon Sunset wrote back to the Princess, and waited by the statue.
Back in Equestria, Twilight prepped her magic mirror, having explained the changes Flash would face at Canterlot High. He was prepared, even though it meant he would no longer have wings. He didn't mind, he wasn't much of a flier anyhow.
He faced the portal, ready to meet the mare he had been in love with since foalhood.
Twilight gave the countdown, and when she said go, he sprinted for the mirror, and as he neared his reflection, he thought he saw it flinch. When he passed through, he was outside, and he was cold. He stumbled to his- Knees? He held his.....hooves to his his face, and saw that they were no longer cups, but they were like Spike's claws with an extra digit. He examined his new extremities, and touched his nose. It was small. It was quite a confusing revelation to be sure, but it was all made better when he gazed up to see Sunset Shimmer staring down at him. All he could do was blush, and look back as she extended her hand to him. Slowly, and reluctantly he gave her his....hand, and uncurled his fingers letting their hands fold onto one another. He found it to be a very fulfilling experience.
She pulled him up slowly to allow him to become stable on his new feet. His knees were weak, and he leaned against her. She was blushing now.
"You really do need some work." She chuckled.
He did too, nervously. "Yeah, but the Princes told me you could help."
"I-I'll do what I can." She said sheepishly as she guided him into the school.
"Well, I think you'll do great." He smiled as he started walking on his own.
Sunset blushed. This Flash was sweet, and looked just like the other one, but there was something different. He carried himself higher than Flash did. Did she really inspire him that much? She was eager to find out.
Back in Equestria, Flash stopped right outside the portal getting aquatinted with his new body. His arms moved okay, and it was weird not having fingers, but the most different thing of all was the wings. They were like extra arms, and that freaked him out, but before he could panic he started to trot very easily on all fours just staring at his wings when he bumped into someone. He turned to see Twilight. The two just started laughing.
"Will we ever not?" He asked.
"No, and I hope we keep bumping into one another." Twilight giggled nuzzling her nose against his. He smiled. "You know, you take to trotting rather well." Twilight complimented.
"Thanks," Flash chuckled."I guess it's some kind of instinct. The only thing are the wings." He said showing them to her.
"Oh, don't worry, I've read up on tons of wings, and flying. I can help you with the basics." Twilight assured him.
"Thanks again." Flash smiled, "Now show me around, what is this place really like?"
"Oh, right, well, follow me." Twilight said confidently as she cantered on to give him the royal tour.
Flash knew he would like it here. It might be a bit "back to basics" like Sunset said, but he was never big on too many techno gadgets anyhow. If there were only acoustic guitars he would be happy. He'd also be happy anywhere Twilight was.
I know this one is long, but this is how Flash and Twilight got together in my headcanon. They just switched places. Ii think it works. That way we have Flashlight, and Sunset Sentry. Everybody wins!