Rainbow Dash groaned as she slowly regained consciousness. "Okay," she muttered under her breath, "note to self: do not experiment with magical artifacts using magical explosions." Opening her eyes, she scanned her surroundings through her suit's optics. "High background magical energy levels...some sort of desert...breathable atmosphere without a trace of civilization generated pollution? Well, one thing's for sure. I'm not in New York anymore." Her eyes widened and she shot to her hooves. "Dad?"
A groan from nearby drew her attention. "Did anyone get the number of that freight train?" he muttered, sitting up. His suit seemed intact, as was hers.
"Dad, I don't think we're on Earth anymore," Rainbow explained. "There's way too much excess magic." Glancing over, she swallowed. "And it doesn't look like transit was smooth."
The desiccated corpse three feet from them still wore the Mandarin's clothes.
Tony stared at the skeletal remains and swallowed. "Well, I guess our suits protected us or something."
"Rainbow!" a young, female voice shouted.
Spinning, Rainbow spotted an orange and purple filly racing towards her. "What?" she asked in disbelief.
The filly screeched to a halt, the scooter she was riding kicking up dust as she stared at Rainbow. "Rainbow Dash? Is...is that you?"
Rainbow stared at the filly. "Are you...Scootaloo?" she asked in confusion.
"Don't...don't you know me, Rainbow?" Scootaloo asked worriedly. "That...that is you, isn't it? The robo-suit's kinda new..."
Rainbow blinked, her face mask withdrawing into the helmet. "Are...are you my little sister?" she asked, confused.
"...sorta," Scootaloo admitted. "What happened to you? You're really...different."
Rainbow scratched her head. "Kind of a long story, Squirt," she found herself saying. For some reason, that made the filly really happy. "Can you tell me what happened on this end? I can probably explain if I get some more details."
Scootaloo tilted her head in confusion, but replied, "Well, we came out here so you could try out this new stunt."
"Stunt?" Rainbow repeated.
"Yeah," Scootaloo replied. "See, I'd written this fanfic about you called 'Double Rainboom', and while Twilight said the characterization was bad, you thought the actual 'Double Rainboom' stunt sounded awesome, and you wanted to try it. But after the explosion of the Double Rainboom you crashed into the ground, and I rushed over to you as soon as it was safe...but you're different."
Tony scratched his head. "I think I've got a theory, but what about you Rainbow?"
"Who's the robot?" Scootaloo asked as other ponies raced up.
Tony's face mask withdrew as well. "I'm not a robot," he scolded. "I'm a human."
"Humans are real?" Scootaloo asked in shock.
"I think we've found your world of origin, Rainbow," Tony pointed out. "But how'd we get here?"
"Well, considering what you told me about how I got to you," Rainbow mused, "I'd say that my performing the Rainboom that shattered the Mandarin's rings created the same energy reaction as this 'Double Rainboom' Scootaloo says I performed, and the nature of the energy released caused the explosions to link, causing the two mes at either end to switch. The only thing that doesn't explain is why I wound up a filly nearly two decades backwards in time."
"Well, one of the effects of the rings is rejuvenation, and another ring has some influence on time," Tony pointed out. "It could be that the rings exploded because the Sonic Rainboom supercharged them."
"And that sent the me from this side of the explosion back in time and reduce aged to a filly?" Rainbow asked. "Then how come the me that came through from Earth didn't end up a desiccated corpse?"
"I guess the magical energy in your power suit protected you," Tony offered, "which caused the energy to recoil on the one closest to the explosion who was both unshielded and attuned to the rings' energies." He pointed to the corpse.
"Which is why the Mandarin is a skeleton?" Rainbow asked. "I suppose that's a viable conclusion..." Rainbow's voice trailed off as she noticed Scootaloo, five other ponies, one tiny dragon, and a tortoise with a propeller beanie keeping it afloat all staring at her. "What?" she asked. "You act like you've never heard someone talk science before."
"Oh, we've heard science talk before darling," the white unicorn offered.
"Just normally it's Twilight talking techy," the orange pony with neither wings nor horn pointed out, gesturing to the purple pony with both.
"Since when did you become an egghead?" Scootaloo asked. "I mean, it's cool and all if you're doing it, but...it's, well, new."
Rainbow blinked. "Dad, what do they mean by that?"
Tony did his best to suppress a chuckle. "Well Rainbow, given we've established you apparently lived an entire life here before winding up with me, I think over here you were a jock."
Rainbow's eyes widened. "What? Say it isn't so!" she pleaded with the ponies. "Tell me I wasn't a big, dumb, jock!"
"Actually, you were always small for your age," the butter yellow pegasus offered shyly.
"And I wouldn't call you unintelligent," the one addressed as Twilight pointed out.
"But you certainly were a super duper athlete obsessed with being the best flyer in all Equestria!" the perky, poofy, pink pony proclaimed as she bounced up and down.
Rainbow wailed as she fell back on her flank. "My life is rui~ined!" The butter yellow pegasus giggled. "What's funny?" Rainbow demanded.
"Well, having known you the longest," she pointed out, "I'm glad to see that, even if you've changed so much...you're still, well, you."
Rainbow blinked. "Not entirely sure how to feel about that." She turned to look at the tortoise that had been banging repeatedly against her helmet. "I...I know you, don't I? I remember..." She scrunched her face up in concentration. "...Tank?"
The tortoise promptly nuzzled her face affectionately before flying dizzily away. And then the sky ripped open around him.
"Tank!" Rainbow and the yellow Pegasus yelled in fear.
When the rip faded and the figure from within appeared, the pink pony screamed in panic. "AIIIIII!!!! GOJIRA!" she screamed in a horrible Japanese accent.
"Actually, his name is Zuki," Rainbow corrected, recognizing the silhouette taking shape.
The pony blinked. "Godzuki?" she asked. Tony facepalmed, finally getting the joke.
Rainbow flew up to examine her 'puppy' and look for her tortoise. However, she noticed something off about Zuki. His shoulders, elbows, and knees all had solid shells in a tortoiseshell pattern protecting them, and his scales had taken on a tortoiseshell pattern. Also, dragonfly wings that resembled helicopter blades of pure magic were folded to his back, six sets in all. "Zuki?" she asked worriedly.
The beast nodded in response.
"...Tank?" Rainbow asked in disbelief.
The massive beast leaned its gargantuan head forward to nuzzle her.
"...Tankzuki?" Rainbow posited.
The fused beast roared in confirmation.
"Didn't see that coming!" the pink pony spoke up. "By the way, since you haven't remembered us yet but you will, let me make things easier on you and Mr. Stark here! I'm Pinkie Pie, and this is Applejack, Rarity, Fluttershy, you heard Twilight's name already, and Spike!" As she spoke, Pinkie Pie pointed to each of the ponies in turn, making things much easier on the narrator.
"Pleasure to meet you all," Tony replied.
"Pleasure to meet you all...again?" Rainbow suggested, landing and withdrawing her suit into the armor belt. She was startled by Spike's low whistle. "What?"
"Dang, Rainbow!" Applejack said in admiration. "What sorta workout have you been gettin' as an 'egghead' to get so toned?"
Confused, Rainbow looked down at herself. While she wasn't aware of it, despite being physically fit and an excellent flyer, in her previous life she had been a bit soft, a product of her tendency to coast and laze rather than push in every area of her life. Growing up to be Iron Mare, however, had allowed for none of that. Between the training she'd had under Thor and others, her own hero work, and the amplification of her magic the suit did, she was a very different specimen. Her wing to body mass ratio was still the same as before, but her wings were much sleeker, each feather fuller. Her frame was also somewhat leaner, with every muscle in her body well toned for flight. Before, she had been a fast Pegasus. Now, every inch of her body screamed speed.
"Well, I guess fighting supervillains, criminals, and an alien invasion make for good workouts," Rainbow allowed.
"What's this?" Twilight asked, looking at the medallion hung around Rainbow's neck.
Rainbow smiled. "If it still works, a good safety net." She lifted the Bifrost badge into the sky.
As the sunlight glinted off of it, it released a beam of white light into the sky. A massive rainbow shot to the ground in response, and Sleipnir stepped out of the bridge. "I see you've found your way home, Rainbow," he said softly. "That is good."
"Wait, you talk aloud here?" Rainbow asked in confusion, compounded when Twilight let out a 'Meep!' and fell flat on her face.
"Indeed," Sleipnir replied. He turned to stare at Twilight. "If you know the record of my time here, Twilight Sparkle, you know how I feel about such obeisance."
Twilight got to her hooves nervously. "Sorry, Great One," she said quickly, blushing at the tongue slip. "It's not every day I meet a living legend of Equestria's history."
Sleipnir chuckled. "Of course it is," he replied easily, "depending on how you define history. You groom your mane in the mirror every morning, don't you?" He turned away from Twilight's embarrassment. "How are my daughters doing?"
"Princess Celestia and Princess Luna are doing just fine," Twilight replied, making the other ponies gasp and fall to their faces, which made Rainbow roll her eyes.
"I see," Sleipnir replied, glowering until the others got back to their hooves. "And what of my brother, Discord?"
"EH?" all five mares, one filly, and one dragonling gasped in shock.
"Oh, did he never mention that?" Sleipnir asked in amusement.
Rainbow chortled. "I don't even know what's going on yet, but I can already tell this is going to be hilarious!" Reaching out, she ruffled Scootaloo's mane. "So the Bifrost is working now?"
"Yes," Sleipnir replied. "Transit between Earth, Asgard, and this world via the Rainbow Bridge is now functional and stable."
"That's a relief," Tony said as he glanced around. "Well, time for first contact." He looked to Twilight. "I'm not sure what to say: we come in peace, take me to your leader, or Bah-weep-graaaaagnah wheep nini bong."
While most present tilted their heads in confusion, Pinkie and Rainbow both burst into suppressed chortles.