Who's More Athletic Than Who?
Undyne cut through more unkempt vines and vegetation with her spear, she was still heaving from that bulky armor she stripped off earlier, leaving her in her traditional tank top and jeans. She had went on patrol through the Waterfall and accidentally slipped in. She struggled to get out but the water kept dragging her down further and further until she fell into the bottomless pit in the Garbage Dump, where she awoke in a pond in the middle of a forest.
'I hope I'm still Underground, she thought to herself. 'There's no forest like this in the Ruins though, and it's so hot here. Feels like Hotland, eugh...' With one final slash she cut through another foliage of vines to reveal a slimmer of sunlight into the dark forest. She grinned as she kept slicing closer and closer to the light until she was free of the forest, the sun shining bright on her face. She grimaced as she covered her eye, but she was filled with joy, though she may be lost she thought she found a way into the human realm that didn't require passage through the barrier, the bottomless pit was the key back to the surface all along! Her eye slowly fixated to the brightness of the surface, she looked around her. A lake with water lazily trickling down it's path, and what looked like a Town off to the distance. She brushed the leaves and muck off her shirt with her claws as she walked towards the Town. 'I hope humans still don't have it out for us freaks, if not maybe I could scare me a couple of 'em, that'd make me feel better.'
Dash lounged on her cloud, letting the sun and the cool wind give the perfect temperature for her break, she'd poof the could right after she was done and go about poofing the others to give Ponyville the perfect sunshine look it always had. She heard water shuffling from right below her, she figured one of the woodland critters came out for a drink or something, that was until she heard somepony talk, she peeked down over her cloud to realize it was no pony, but some other creature.
"Man Alphys is gonna love to hear about this, she'd be bummed to stop her barrier research though, poor nerd," Undyne said to herself. Undyne saw something pop out of one of the few clouds in the sky, what looked like a horse's head with a multi-colored mane. 'Am I going crazy, or is there a blue horse on a cloud in the sky?... Man the human realm is a lot more different than what I had expected, why'd Alphys leave out cloud-horses when she was telling me about the Surface? That sounds friggin awesome!'
"Whassup horse-cloud!" the strange fish creature bellowed, making Rainbow Dash jolt in surprise. She assumed the fish was talking to her, as strange as she was Dash wasn't one for keeping company waiting, she took a quick stretch and flew down to greet what might possibly be the weirdest creature she'd ever saw in her life. Dash examined the creature for a brief moment as she fluttered down. Such a strange posture, she was truly puzzled on how it was keeping balance using only two legs, and the other two had these weird little appendages on them that gripped an insanely wicked blue spear. Her eye's looked like that of some reptile, well the one working eye that is, the other had an intimidating eyepatch over it. And her blue skin, it looked so rough and scale like, with multiple streaks along her arms and some visible parts of her torso of what Dash can only imagine are previous battle scars. Dash touched down just a few feet away from her, her left hand propped on her hip with what looked like an attempt at a friendly grin, but the ferociously sharp teeth said otherwise. "Huh, you aren't a horse-cloud, just a horse? Bummer, nice wings though."
"Thanks," Dash replied, flexing her wings. "Nice spear."
"Meh, I left my better one at home," Undyne yawned as she twirled her spear nonchalantly. "So, this is what the Surface is like huh? Not bad, but I think Alphys was teasing me about what it's really like."
"What?..." Dash asked, genuinely confused.
"Oh that's right, you don't refer to it as the surface, it's just the earth to you. C'mon, you telling me you don't know about the war between us and humans?"
"What do you mean by us? And no I haven't heard of that war, what's a human?"
"Aw crap, I don't think I'm on the Surface OR the Underground. Great, now I'm lost in some other realm that I know nothing about!" Undyne croaked, looking panicked.
"Well just to tell ya, you're in Equestria. That ring a bell?"
"No it doesn't. Nor do flying horses, the only flying talking horse I ever seen was Aaron. And he doesn't even have legs, he has fins, with huge beefy arms!" Undyne was really starting to panic now, what if she could never get back home? What if a human managed to fall down in Underworld, how was she going to stop it? And worst of all, she wouldn't get to admire Alphys' butt anymore!
"You alright? Uh... maybe I should ask Twilight about this, she should be able to you help you out. She's never met a pony she can't help!" Rainbow Dash said with a weak chuckle, trying to make the fishy figure not so upset.
"Well I'm NOT a pony! And I doubt someone can make a ladder with infinity step on it to get back up from where I came! Even with my legs that's a climb even I'm not looking forward to."
"Ah, you like to work out too?" Dash jested, she may have just found a way to get this monster to calm down.
"Pshh, heck yea! There's not a minute that goes by without me thinking of bench pressing something. I could probably bench press about fifteen of you, twenty if I carbed up some before hand."
Well that worked surprisingly well, though Dash had no idea what the hay she was talking about with 'bench pressing', at least it took her mind off the 'Underground'. It was odd, Dash saw a lot of the same properties in this monster as she did herself. Well aside from the two legs, the teeth, and almost any other physically property other then a love for strength! She had an idea, to distract this creature and tell Twilight about her to help her get back to her realm. She began brainstorming time consuming exercise junk. Jogging, walking, running... not much exercise after all, perhaps she could do whatever this 'bench pressing' thing is.
"So, how many of me you think you can bench press?" Undyne teased.
"Huh?" Dash asked, forgetting she was just staring blankly at the creature while deep in thought. "Uh, I dunno. Maybe ten of you?"
"Pfffft, haha! As if. You couldn't even lift one of me!"
"Oh really?" Dash asked. She didn't know why this creature teasing her about an activity she didn't even know was annoying her, but it was. "You wanna bet?"
"You're on!" Undyne shouted, followed by a menacing smile. Dash and her locked eyes, neither one moved for the longest time. "Aren't you going to... ya know, get into position?"
"Of course!" Dash laughed, though she had no idea what to do. She thought a guess out be better than nothing though, she stood on her back hind hooves and held her front two out and Undyne.
"I knew it," The scaley fish lady laughed. "You don't even know what bench pressing is!" Rainbow Dash flustered up brighter than Fluttershy getting hit on.
"Well if I knew how then I bet I'd be pretty good at it!" Undyne stopped laughing, or at least tried to as she kept snickering. She playfully pushed Dash onto the ground, took her front two hooves and held them towards the sky, and started to run away from Dash. "What're you doi-"
"BETTER BRACE YOURSELF, PUNK!" Undyne bellowed and she charged at Dash. She took one good leap, almost soaring over Dash, but landing perfectly in Dash's hooves. She almost gave out at the pressure of the impact, but her shaky hooves managed to keep Undyne in the air. "Wow, you're tougher than I thought. Still, this is just one of me, you said you could life ten. Still think you can?"
"Uh... O-on second thought, n-no." Dash heaved. It took all her concentration just to hold this fish face in the air.
Undyne laughed. "Wow, you can barely even lift me up? I can suplex boulders like six times your size, punk. That means you forfeit, that's one point for Undyne!"she declared as she lounged atop of Dash's still quivering hooves.
"Oh so now it's a contest huh? Well you may be stronger, but I bet I'm faster," Dash replied. Asking Twilight for help could wait, for now she was about to kick this fish's butt!
"Ha! I'll admit your wings are nice, but no one could beat these legs!" Undyne said triumphantly as she hopped off Dash's hooves.
"We'll see about that. We'll race... to that rock!"
"There's more than just one rock around here," Undyne groaned as she looked around. "Which one?"
"The one that looks like a butt."
"Ah, I see it. READY SET GO!" Undyne roared as she ran off full speed at it.
"Cheater!" Rainbow Dash yelled, and soared at the rock as hard as her wings would flap. She was easily gaining ground on Undyne, if Dash wanted to she could easily cut her flying speed in half and still make it, but she wanted fish face to eat her dust.
Undyne charged at the rock, she was almost there. Another victory just within her grasp. 'Horse thinks she can beat me, we'll see about tha-'. Her thought cut short as a huge gust of wind wafted over her, knocking her to the ground face first. She peeled her face off the ground to see Dash standing atop the butt-rock, smiling contently. "No fair," Undyne mumbled, "You knocked me down."
"Well you ran ahead of me!" Dash protested. "I still get a point."
"Whatever, I'll still kick your butt at the next cha-"
"Undyne?! U-undyne!" a squeamish noise called out. Undyne remembered that voice from anywhere, Alphys!
"Alphys!" Undyne called back, looking into the thick forest, "I'm over here!" A huge whapping sound could be heard, as well as some sort of engine. Just then a buzzer mini-copter popped out if the tall trees from the Everfree forest, a dweebish yellow dinosaur in a lab coat operating it. Dash stood there jaw dropped as Undyne cheered and hopped in delight. "You finally got that thing working!" she cheered as Alphys touched down right beside her. Alphys hopped off the buzzer and ran over to Undyne, she wrapped her claws around the fish's waist.
"I was so worried w-when I saw you f-fall into the pit. I thought I'd n-never see you again!" Alphys stammered.
"Calm down, as you can see I'm still as cool as ever with every bit intact," Undyne replied, calmly petting Alphys' head. "But wait... how'd you see me fall down the falls, and more importantly why'd you not help?!"
"Well a-a-about that..." Alphys began, pulling away from Undyne, "I kinda sorta... k-keep a camera hidden in your armor... S-so I can keep an eye on you, o-of course!" Alphys explained.
"I knew you keep cameras around Underground, but my armor? Seriously!? That's... awesome! You can capture all the battles I do in them!" Undyne replied. Alphys half expected her to scold her, but this was unexpected.
"Well t-the camera's sorta... on the b-buttock inside piece of the armor." Alphys murmured to herself.
"What's that?"
"I s-said it's good to s-see that you're okay!" she quickly replied. Alphys turned her attention from Undyne to Rainbow Dash, then the area surrounding them, "Interesting, so the bottomless abyss leads here. That debunked all my observations and theories. B-but it's good to know what's down here now. I'll be sure to come down here again soon to study it some more."
"Yeah! And I'll come with you," Undyne replied, then turning her eyes to Dash, "Our contest still ain't over."
Dash smirked, "Far from it." Undyne and Dash waved their goodbyes as the two creatures took off back to the entrance of Underworld.
Dash sighed as she escalated effortlessly to the cloud she was on earlier. She touched the soft fluffy clouds and lounged deep into the cloud's puffs, her eyes closed. Only to have them shoot open as she heard Undyne, still within ear distance, shout, "LATER PUUUUUUUNNNNNNNK!"
Author's Note
This took longer and also was longer then expected. I was afraid it would turn into a 2-part story 
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I don't know what mash-up I might do next, needless to say I will be doing another one, if this one gets good reviews I mean. I'm really enjoying writing these mashups, though sadly, just like FNAF, Undertale hype will soon fade away. So let's enjoy it while it lasts 
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Hope you enjoyed the story, please remember to like if you liked it, or to dislike if you didn't like it. That way others can see if it's any good or not. Which it really isn't... heheh...
