Subverting Expectations Since Day 1
"Hmm hmm hmm hmm hmm hmm hmm hmm hmm, hmm hmm hmm hmm hmm hmm hmm..."
Rainbow Dash was peacefully humming Cloudsdale's national anthem to herself as she mopped up the floors of the barracks. She still had memories of hating this job when Spitfire first foisted it upon her, and if she was being honest, she still didn't like it. But after a few days working alongside her idols and participating in actual military life, she had accepted that this came with the territory. Especially after she made such a fool of herself in that last performance.
"Annnnnd, done," she said, taking a look at the clock on the wall. "Yes! Just under fifteen minutes! That's a new record! I bet Captain Spitfire would be really proud of—"
"SURPRISE~!"
"Gah!"
Rainbow Dash was startled out of her wits when somepony came out of nowhere and screamed right in her ear. She darted up into the air, causing cleaning chemicals to spill everywhere. When she calmed down, she saw that the culprit was none other than one of her fellow Wonderbolts, Surprise. She was wearing a large goofy grin; one that reminded Rainbow Dash too much of Pinkie Pie. Rainbow scowled.
"Ugh, what's wrong with you, Surprise?" she growled. "I just got finished cleaning! Also, whatever happened to Wonderbolts not getting super enthusiastic?"
Surprise giggled. "Sorry 'bout that, Crash. But just so you know, this is kinda my thing. Besides, we're not all straight-laced and super-serious all the time. We can have our moments, just as long as we don't go overboard."
"Uh-huh," said Rainbow Dash with a slow nod. "Still, this is the third time you've done this to me. You're not singling me out on purpose, are you?"
"Oh, nonononononono," said Surprise with a shake of her head. "I do this to everypony."
Rainbow blinked. "Seriously? And Captain Spitfire doesn't get mad at you?"
"Only when it gets out of hoof," said Surprise. "Moderation is the key, young Crash-hopper." She giggled at her own joke. "Tee hee~! See what I did there? Crash-hopper? 'Cause your nickname is—"
"I get it, I get it," said Rainbow Dash, floating back down. "Y'know, I still have a lot of baggage tied to that nickname. It's, still gonna take some getting used to."
Surprise's expression suddenly became serious and contemplative. "Trust me, Rainbow Dash. I've been there," she said solemnly. "All of us have. But really, if you had a problem with that name, you should've told the Cap directly. She might be our leader, but she's not the best at reading ponies."
"Yeah, I was pretty dumb. You don't have to remind me," said Rainbow Dash sheepishly. "That's why I'm stuck cleaning these stupid barracks in the first place."
"Mmm," said Surprise with a nod. "But like I said, you're not the first. Personally, I don't really blame you. We're the best flyers in Equestria; getting accepted into our ranks is no easy feat. And once you do get accepted, you put all this pressure on yourself to make a good impression, and then something goes wrong, and everyone else razzes you for it."
"Heh, I sure learned that the hard way," Rainbow Dash chuckled. She then started mopping up the spill. "Hey, Surprise?"
"What's up?"
"Your callsign is Slowpoke, right?"
"Sure is."
"Why do they call you that?"
Surprise tilted her head. "What to you mean?"
"I mean, I've seen you fly, and I've seen how you act around the barracks," said Rainbow Dash. "You're not really a slowpoke. If anything, you're more like a ninja, always sneaking up on me."
"And everypony else," Surprise added.
"And everypony else," Rainbow Dash conceded, clearing her throat. "Plus, when you're not flying, you seem so happy and energetic all the time. Almost like a restrained version of somepony I know back home."
"You mean Pinkie Pie?"
Rainbow Dash's eyes went wide. "How do you know—?"
"Well, duh! Any party pony worth their salt knows who Pinkie Pie is!" Surprise chirped.
Rainbow Dash did a double take. "Wait, wait, waitwaitwaitwaitwait. You're a party pony?!"
"Born and bred," said Surprise proudly. "Here, take a look."
She removed her uniform and pointed to her flank. Indeed, her Cutie Mark was nothing Rainbow Dash would've expected from a Wonderbolt. Instead, it was a trio of purple balloons, arranged similarly to Pinkie Pie's Cutie Mark. Rainbow's jaw dropped.
"Okay, now your callsign really doesn't make sense," she said. "If you're like Pinkie Pie, how'd you get the nickname Slowpoke? 'Cause let me tell you, when I think of Pinkie, the last thing I picture is a slowpoke."
Surprise blinked a few times before a realization seemed to hit her. "Oooh~! I see why you're confused," she said. "Well, there's actually a very good reason for my callsign."
"Oh, this I gotta hear," said Rainbow Dash, taking a seat on her bed.
Surprise cleared her throat. "It's like this, Crash. Do you know what 'surprise' means?"
Rainbow Dash gave Surprise an odd look. "Um, when something you didn't expect to happen happens?"
Surprise smirked. "You catch on pretty quick, Crash-hopper. Thing is, I'm not just some goofball pony. But back when I was a party pony, that's how everyone in Cloudsdale knew me. I was the silly clown always sneaking up behind folks yelling 'SURPRISE~!' left and right and giving ponies a good laugh. And I liked that, of course. It's what I was meant to do."
She then looked over at her bunk, which had Wonderbolt posters on the wall. "But I had dreams beyond that. I didn't just want to do the same thing over and over again. Then it wouldn't be surprising. It'd just be, ordinary. So, I signed myself up for the Wonderbolts, just to throw ponies for a loop."
Rainbow Dash raised an eyebrow. "Seriously? That's the only reason you're in the Wonderbolts."
"Oh, not the only reason," said Surprise. "You've seen me out there; I'm a pretty good flyer, too. I knew what the Wonderbolts represented, and I genuinely did want to be a part of that. Subverting expectations was just a bonus."
She then sighed. "But then, I overthought things."
"How so?" asked Rainbow Dash, leaning in with interest.
"My first day, I really wanted to show the 'Bolts just who I was: An unpredictable wild card of a pony who wasn't just some clown. During our first tryouts, I deliberately took things nice and slow. Y'know, slow and steady wins the race and all that."
She let out a bitter laugh and shook her head. "But the problem was it wasn't a race. What's more, nopony really knew who I was. I mean yeah, Spitfire had my history in some dossier somewhere, but she never met me in person before. I found out the hard way that it's pretty difficult to subvert expectations when other ponies don't really have any expectations of you."
"Wow." Rainbow Dash furrowed her brow. "What happened then?"
Surprise shrugged. "Well, for each run, I kept lagging behind. I kept resisting the urge to be my usual, cheery self because I didn't want others to think that's all I was. Eventually, somepony, I forget who, yelled at me. I won't forget her words." She tapped her chin. "Or, maybe it was a stallion. Again, don't remember. But they said to me:
"'Hey, pick it up, slowpoke! You can't be a Wonderbolt if you get left behind!'"
Rainbow Dash flinched. "Yeesh. That, sounds kinda mean."
"It does. And it did hurt," Surprise admitted. "Much like you, I just tried to play it off. After all, I was still trying to avoid being the class clown. But then, I got, the Jacket."
"The Jacket?"
"My new nickname was plastered on my uniform for all to see. I was Slowpoke for life, even though that was just an act." A soft smile cross Surprise's face. "When that happened, I couldn't help myself. I laughed so hard, ponies could hear me clear across the runway. When Spitfire asked me what was so funny, I told her that Slowpoke was probably the least-fitting nickname anypony could give me."
"So, you ended up hating it?"
"A bit, yeah. When it turned out she was serious, I just got knocked off my hooves. I tried so hard to avoid an embarrassing nickname based on my past as a party pony that they gave me one based on me trying so hard to avoid a party pony nickname. How's that for a melon scratcher?"
"Yeah, it's pretty hard to follow," Rainbow Dash confessed, rubbing the side of her head. "But you're cool with it now, right?"
"Yeah, but man, was I embarrassed," said Surprise, blushing profusely. "I really should've just been myself, y'know? Being called a slowpoke was just a reminder of how, fake I acted. Kinda like when you acted all weird on your second day."
"Ugh, don't remind me," Rainbow Dash groaned. "Seriously, why did I think imitating my friends was a good idea?"
"Don't ask me; I'm not you," said Surprise with a shrug. "Oh, just FYI. Don't do the 'wake everypony up at the crack of dawn being super happy' routine ever again. That's my schtick. And I usually wait for after the call of reveille."
"G-got it," said Rainbow Dash with a hasty salute.
Surprise cleared her throat and continued her story. "Anyway, I did kinda sulk for a while after that, ironically living up to the nickname that didn't fit me at all. But then, Misty Fly said something to me."
"What'd she say?"
"'So, your callsign's Slowpoke, huh? Odd nickname for a pony named Surprise.'"
Surprise's face suddenly lit up like a Hearth's Warming tree. "It suddenly felt like the gears in my brain were going into overdrive. Surprising ponies is all about subverting their expectations! And I just gave the Wonderbolts the biggest surprise of their lives! The nickname Slowpoke fits me because it doesn't fit me! And figuring that all out made me feel so super good, I could fly circles around the barracks for hours!"
Rainbow Dash blinked. "Huh. So, that's why they call you Slowpoke?"
"Pretty much," said Surprise. "It doesn't make much sense when you think about it, but that's kinda the point. I'm a mare who keeps you guessing. There's no telling what I'll do or when. Plus, it's a nifty little reminder that I should be true to myself."
Rainbow Dash nodded. "Huh. Okay then." She then chuckled. "Well, at least you didn't try to force a new nickname like I did."
"Yeah, that never works. Just asked Dizzy Misty," Surprise said with a laugh. "Well, I should probably get back out there. Looking forward to flying with you once your probation's up, Crash-hopper."
"Same here, Slowpoke," said Rainbow Dash with a salute.
Surprise saluted in return and took off out the door. Rainbow Dash smiled and turned back to the spill she made. Her smile faded, and she let out a sigh of resignation.
"Looks like it's gonna be another fifteen minutes before I can head home," she muttered, starting to clean again. "Still, I knew these guys were cool for a reason. It's just, not the reason I expected."
"Would you say it was, surprising?"
"Dah!"
Rainbow Dash jumped again as Surprise showed herself in the doorway. She groaned.
"Surprise~!"
"That's my name; don't wear it out!" Surprise giggled. "But most Wonderbolts call me Slowpoke. Weird, I know. Anyway, see ya, Crash-hopper!"
Rainbow Dash scowled as Surprise left, but once she was gone, she couldn't help but chuckle to herself as she got right back to work.
Author's Note
Guess who's back, baby! 
Anyway, I notice everyone making stories about Spitfire's callsign, but I kinda wanted that to remain a mystery. Instead, I wanted to explore why Surprise, a pony who inspired the creation of Pinkie Pie, got a frankly ill-fitting nickname like Slowpoke. Though I still call her the Queen of Unpredictability, at least when it comes to her portrayal in my stories. 
