Rainbow weakly opened her eyes to see white. Hospital ceiling white. In her half-awake daze, she let out a "fweet" from her rear without thinking.
It was greeted by giggling coming from between her legs, in a familiar voice. Twilight's voice...but sounding a bit off, like it was mixed with Snails'. "See Rarity, she always farts when she wakes up! I win the be-et! 5 bits, 5 bits, 5 bits!"
Rainbow sat up to look, seeing first a stallion doctor to her left, then Princess Luna, then Twilight between Rainbow's legs on the edge of the bed, then her four friends and Spike to the right.
Rarity scoffed. "I never agr-" she began to say in outrage, but Applejack put a hoof in her mouth.
"I'll give Spike the 5 bits to cover Rarity, Twi." Applejack replied.
As Twilight cheered and fell over, Rainbow felt her neck with a hoof. There was definitely a scar there. "So, you saved us...but what happened to Twilight?"
Luna stepped forward. "We had to save you first, and it took some time. Alicorn brains are special, they stay alive with magic long after oxygen is cut off, and they prioritize losing less...important brain cells." she began to trail off towards the end, staring at Twilight doing an uncoordinated potty dance and talking of having to pee. Pinkie was joining her, while Rarity and Fluttershy seemed rather put off.
Spike made a snarky reply gruff voice. "I don't think she had all the ones she needed to begin with, but...I'm glad she's alive. Worst month of my life."
The doctor cleared his throat. "Her rate of cognition, bodily control, and impulse control were all damaged. Your friend will need quite a bit of help to live a normal life in her current state. I'll make sure to do regular checkups on her. I'd also like to give you one such checkup, to determine if you've lost anything from your brief time unconscious."
Rainbow nodded and stared as Rarity led Twilight with Spike riding her out to the bathroom, followed by the doctor. She looked to Luna. "Has this happened before?"
Luna nodded. "A few times. If Twilight is like Celestia, she'll be back to normal in a few years, 4 at most."
Pinkie cartwheeled over to Rainbow's left side, then leaned on the bed with a hoof. "So, where is Celestia? Is she dead? Did she miraculously escape some deep cave underneath Canterlot that's never been seen before or since?"
Luna sighed. "I'm afraid my sister was forcefully drained of all useful information and emotion by Chrysalis. While she can move the sun, her memories are in tatters and her personality is barely there. She does at least recognize me, but it could be decades before she's back to normal, at least one before she can rule on her own."
"That's awful!" said Fluttershy.
Luna just nodded. "I will be there for her, as well as ruling Equestria."
Pinkie then did her best to ruin the drama of the moment. "So Rainbow, you gonna have fun with Twilight like you did before our execution later? I've got a biiig 'welcome-back-from-being-decapitated' part planned!"
Fluttershy and Luna obviously weren't prepared to answer, their faces showing discomfort.
"Uh, Pinkie, it wouldn't be right to take advantage of her like that. I don't know if she still understands what sex is." Rainbow replied.
Applejack trotted over to the bed. "Sugarcube, she might be dumb, but, honestly...and no offense, she ain't that much dumber than you. I'd say, if anything, the relationship's actually more equal on intelligence than before."
"Wow, that was harsh, Applejack! Somepony should call the fire department, cause this pony just got burned!" said Pinkie, finishing with a rise in pitch from excitement before giggling.
Rainbow was trying to process it when Luna spoke up. "My little ponies, it is on all of you to help Twilight Sparkle recover, and if you limit her due to her lower intelligence, you will only stifle her instead of help her. She deserves the same chance at love as everypony else, and I do not believe she'd support treating her like that, especially since she made the decision before to date Rainbow, as Applejack pointed out. I therefore recommend to you, Rainbow Dash, that you continue your relationship with her, perhaps just somewhat more carefully. With that, I must depart." Luna trotted out, leaving everypony momentarily speechless.
Rainbow still wasn't sure. "Well..."
"Sugarcube, listen to the goshdarn princess. And don't do what ya did to me to Twilight, or I swear you'll find apples where the sun don't shine." said Applejack, while Fluttershy nodded.
Rainbow nervously giggled, it was going to be an interesting few years.
A year later, Rainbow was returning from a long day practicing flying with the Wonderbolts. She found Twilight in their room reading a book on taxes, seeming a bit frustrated. "Gah, you know, I never really understood how you felt about this stuff until now, Rainbow."
Rainbow smirked. "Well, it's good to see you've almost caught up with me. I almost want to say you should stop now, so I don't have to become the dumb one again." she said with a giggle before kissing Twilight's cheek.
"Aww, Rainbow, you don't have to be smart to be special to me." replied Twilight.
Rainbow hugged her. "I know. I guess I just miss the way you looked up to me as you came to me for help organizing your own library. Especially when you had trouble even reaching the toilet in time."
"Didn't you find that annoying after a while?" asked Twilight, smugly.
"Well...okay, yeah, but in hindsight, I miss it! And Spike was the one who had to use the mop, not me." replied Rainbow.
Twilight giggled. "Just don't chop my head off to make me dumb again. I think Spike would kill himself." she said jokingly.
Rainbow giggled. "Okay, but you're doing the taxes, since you seem to know them better already."
"My knowledge never left me...I just couldn't really wrap my head around it anymore. I still struggle with a lot of it. Oh, and don't call me 'egghead', okay?" said Twilight.
"Fine, fine. I'll just find a new and better word to tease you with!" replied Rainbow with a smirk.
Twilight rolled her eyes. "Suuuure, and I'll just find a new theoretical basis for teleportation spells."
"You know, at least you got a better sense of humor from all this." said Rainbow.
"I don't know about better...a lot of ponies think I'm a little immature now." replied Twilight.
Rainbow dismissed the notion by blowing a raspberry. "If putting fast-acting laxatives in Celestia's cake at an event about how she's able to function now is immature, I don't want to be mature. So what Luna put you under house arrest for a month?"
The two giggled, and got into bed, hoping their relationship would never end.