The snooty unicorn, Sublime Soirée, looked down her nose at Pinkie. She shook her head slowly. "You wouldn't want to attend this function.This particular party is quite… discerning.”

"I can discern with the best of 'em!" argued Pinkie. "It's a birthday party, right?"

"Mmm, yes, it is," agreed the mare reluctantly. "But, being a birthday party, you have to wear a birthday suit, or you will not be allowed in."

Several of the other highbrow ponies in the room snootily snorted their amusement.

Pinkie tilted her head. “There’s a… suit for birthdays?!” She gasped loudly. “How could I not know this? I am Ponyville’s premiere party planning pony! How could I go all this time being unaware of what to wear to a birthday?!”

The other ponies started snorting more loudly.

Pinkie grabbed Sublime Soirée by her head, pressing their snoots together. “You have to tell me. What’s a birthday suit?!”

Sublime pushed Pinkie off, then smirked and scoffed. “If I have to tell you, you’ll never know.”

Pinkie's expression fell a moment before she perked right back up. "Challenge accepted!" She was gone, leaving a smoky outline that had her basic shape. Even as it faded, the unicorns glanced among themselves, perhaps wondering if she would return, and in what fashion.

"What do you figure the odds of her return are?"

"Ten bits," replies a mare with a cocky smile. "Ten bits says she figures it out and thinks that's good enough for entry."

Pinkie pronked pleasantly through Ponyville, pondering her predicament. How could she never have heard of this?! Nonetheless, she cannot be daunted by a totally out of left field challenge like this.

She would discover what this birthday suit was, and she would return victorious!

If only she knew who would know…

Twilight Sparkle might know! She knew many things. Perhaps she even had a book about birthdays that Pinkie didn’t know about! Pinkie hopped toward the crystal castle.

When she reached the tall doors of Twilight's castle, she raised a hoof as if to knock before she remembered to just push the door open. Twilight never locked them, and she was a friend, so no harm! "Twilight?! Are you there? I have a super mega ultra question." She bounced forward, looking around for the purple princess.

She pronked through the castle, looking through the doors.

Nope, that was Starlight and Trixie doing something weird with a stuffed animal.

Nope, that was Spike staring at a pillar, drooling. Wonder what that’s about?

Nope, that was Rainbow Dash trying to hide in the library, with a book with Daring Do tied up in it.

Aha! Here she was! Studying in the other library!

“Twiiiiliiiight!” She called out, bouncing onto the table Twilight was studying at. “I have a supermegaultra question that needs answering!”

Twilight looked at her research, now scattered, and sighed. “What do you need, Pinkie?”

“Have you heard of a super special suit you wear to birthday parties?" Pinkie giggled trying to imagine what kind of fantastic feat of fashion would just scream 'Happy Birthday!'. She wondered if it literally had that written all over it. That would be amazing!

"A special suit just for birthdays?" asked Twilight with some puzzlement. "I can't… say I've heard of fashion quite that specific. Have you asked Rarity? She is the expert on the matter. I doubt it would have 'happy birthday' written on it quite like that. I'd remember that."

Pinkie blinked. Had she said that out loud? What Twilight said suddenly clicked and she gasped loudly. “Rarity?! OF COURSE! how could I forget the fashioniest pony that ever fashioned anything fashionable! Of course she would know all the weird fashion traditions that the upper crust have! She practically invented a few of them!”

Pinkie pronked out of the castle, looking for her fashionista friend.

“Rarity!” She yelled as she burst into Rarity’s boutique. “I have a fashion emergency!”

The Fabulous Fashionista herself poked her head out from behind a ponyquin. “Oh? Oh dear!” She practically pranced out. “A fashion emergency?! How exciting! Is there a sudden dance? Are you planning to be whisked off of your hooves by a stallion? Perhaps a sudden dance competition has you flummoxed?” She put her hoof to her chest. “Rarity is here to help you with your fashion problems! I am so excited you came to me first.”

Pinkie laughed nervously. “Yeah… first.”

Rarity cantered towards her friend with a bright smile. "Now tell me all about this predicament, darling, and we'll soon have it to rest. There are very few problems that can't be addressed with proper attire."

"That's exactly what I was worried about!" Pinkie bobbed her head quickly. "I need a suit for a birthday."

Rarity's joyful expression only warmed. "Oh, just that? I can have something whipped up in no time at all, dear. Whose birthday will this be for? You simply must have a suit that reflects well on them."

Pinkie tilted her head. "No no, it has to be a suit just for their birthday."

Rarity looked a little befuddled at that. “I’m not… sure what you mean?”

Pinkie hopped. “I need you to make me a birthday suit!”

Rarity paused a moment, and blinked. “Pinkie… that…”

Tapping her hooves excitedly, Pinkie continued, “Can you do it? Can you can you canyou? I need ponies to see me in my birthday suit!”

“Oh” Rarity’s expression flattened. “I know what this is. This is a joke, isn’t it?”

“Whaddya mean? I just need to show up in my birthday suit!”

“Yes. Yes, Rainbow Dash put you up to this, didn’t she?” Rarity sighed and walked back to her work.

“But Rarity, this is a fashion emergency…”

Not looking back at Pinkie, Rarity let out a little harumph in her annoyance.

Pinkie sank to her haunches a moment. If Rarity wouldn't help her get a Birthday Suit, who would?! She raised a hoof to her chin, tapping it. She would not give up so easily.

“Weeelll… Rarity said Rainbow Dash would have put me up to it… so maybe she knows something! And I know where she is!” she sang.

She popped up behind Rainbow Dash, “Hi Rainbow Dash!”

Rainbow Dash snapped the book she was reading closed. “What, huh? I-I-I-I wasn’t reading anything! Certainly not this story!” She twisted around to Pinkie, tossing the book behind her back. “Pinkie! Hi! What’re you doing here where I’m not reading anything?”

Pinkie narrowed her eyes at Rainbow Dash for a moment.

Looking to both sides, Rainbow Dash wiped a bit of sweat off her brow. “D-did you need some help?”

“I sure did!” Pinkie sprang up, her previous apparent suspicion gone. "I heard that there's a really special outfit you only wear to birthdays and I was hoping maybe you knew where I could get one?"

Rainbow barely held back a snort. "Ah, yeah, I've… heard of that. It's really exclusive and stuff, you know? I bet even Rarity couldn't make you one."

“More like wouldn’t” Pinkie scoffed.

"Aw, don't be too hard on her. Like I said, it's really hard to make. I mean, the most a pony will ever have is one of these babies." She snickered, trying to hold it in as she spun her pun. "Why, the emergence of the Birthday Suit is always cause for celebration!"

“So some ponies have parties for these Suits that they wear to parties?” She asked flabbergasted.

"Yup," Rainbow agreed easily, tears escaping her eyes from the mirth she held back only by a hair's width. "It's a really big deal! I'm surprised you don't know about it already."

“I am as well Dashie, this is a complete mystery.” Pinkie Pie nodded sagely. “So! What is it? Tell me tellmetellme!”

Rainbow cleared her mouth, really trying to stop herself from laughing. “Okay, okay, I’ll level with ya…” She leaned over to Pinkie’s ear, and somehow managed to not laugh all the way through her explanation.

Pinkie gasped. “Really?! I never knew that but it sounds funnerriffic! I’m gonna go get that riiiight now!”

As Pinkie hopped away, Rainbow Dash finally burst out laughing so hard she was crying. She laughed and laughed. “Oh man… I wish I was there to see everypony’s faces.”

Soft refined music filled the air as Octavia and her compatriots labored to create the proper atmosphere for the party that was already in full swing.

Many refined unicorns stood around, conversing amiably over floating flutes of wine as they congregated around the birthday stallion, Prince Blueblood. "You're looking even more dashing," complimented one. "You're like a fine wine, only improving with every year." The crowd laughed in comradery at the sentiment.

Sublime Soirée looked on with appreciation. She was Canterlot’s canny celebration creator, after all. And this celebration was her masterpiece. The ambiance, the accoutrements, the accents! Oh it was just perfect. Perfect for the twenty-ninth birthday party of his majesty.

The third twenty-ninth birthday party, if Sublime recalled correctly.

A commotion disrupted the carefully cultivated celebration with a calamitous cry from the entrance. "I'm sorry, miss…" explained the doorguard, but the source of the disruption cared little for the words.

"I am dressed for this party," insisted Pinkie before giving a loud suck on her binkie. Her foal's bonnet fell into her eyes and she pushed it up out of the way. "I got a birthday suit, just like she said I had to!"

“Oh sweet Celestia, she’s wearing a diaper too,” Sublime muttered to herself, before rushing over to the pink pony. “No, no no no no no.” She tried to push Pinkie out. “You have to leave.”

“Nuh uh! I spent all day figuring out what to wear for this party and I am going to go to this party, missy!” She planted her hooves strong, resisting Sublime’s push.

Sublime tried with all her might to push, pushing Pinkie back just a few inches. “Miss Pie you have to leave. If you were not dressed correctly before you certainly aren’t dressed that way now.”

“No! I heard you were the supreme soirée sorter! The amazing amusement arranger! The bodacious banquet begetter, and I wanna see how you run your most fantasticest party!”

Sublime gasped and lost her concentration, and Pinkie bowled her over, the two of them landing in a pile on the floor… and definitely disturbing the partygoers, who all gawked at the center of the floor with a mare dressed like a baby on top of their party planner.

Blueblood looked down at the two that had landed right at his hooves. "I say… aren't you… her friend?" He wobbled a hoof in a slow circle. "Sparity or something like that?" A light smile spread on his face. "I see party crashing runs thick in your little… gathering."

Pinkie rolled up to her diapered haunches. "Oh, hey there! You're the Birthday Boy, right? Where's your Birthday Suit?" She leaned left and right, as if viewing Blueblood from the right angle would reveal the suit to her eyes. "Did you forget it? Oh gosh, I won't tell, promise!"

Blueblood sputtered. “My Birthday Suit?”

Pinkie gestured to her diaper. “The birthday suit, silly!”

Sublime, who was pulling herself off the floor, scoffed. “Miss Pie,’Birthday Suit’ means wearing nothing at all. Because when you are born you are wearing exactly that, nothing.”

Pinkie looked around and at the party goers, who all had suits and dresses on. “So… there’s no dress code? But everypony is wearing fancy stuff.”

“That, Miss Pie, is because there is a dress code.” Sublime straightened her own dress from her tumble on the floor. “As any Canterlot pony knows, a birthday party for Prince Blueblood requires his party goers to wear only the finest wear.”

Pinkie tapped at her chin softly. "Huh, wonder how Dashie got so misled. Don't worry, I have this under control." She pulled a shower-ring out of nowhere, the curtain surrounding herself and Blueblood in an instant, showing more magic than many of the unicorns there. "Birthday suits, coming up!" She threw off her foalish attire, though kept her binkie dangling in her snout. Blueblood barely had time to start complaining before she was on him, stripping him down to his fur without hesitation.

Blueblood flushed red as his coat was revealed… to be the exact same color as the suit he was wearing.

Sublime gasped. “M-miss Pie! That is the Prince!”

Pinkie Pie spat out her binkie into the pile of foal clothes. “And? I made sure he was wearing his Birthday Suit! You should be next. We could get this boring party started!” She started pronking to another pony.

“Pinkie Pie!” Sublime Soirée slammed her hooves on the ground loudly. “How dare you come in here dressed up like a foal, tackle me, strip my guest naked, and and then have the temerity to call my party boring!”

Pinkie stopped mid pronk. She looked around at all the ponies, who were all some manner of nervous or angry at her. Her mane lilted as she fell directly down. “I… I really… I really came in here and did all that…”

Sublime stomped over to Pinkie, looming over her. “This is a fancy soiree, not a… bash, or a party, or anything! We were enjoying a good time socializing and listening to the music!”

“You… you all were? But… but how?”

Quite out of nowhere, a musical bow struck Pinkie right on her nose. "Not. Again," spoke Octavia with no space for uncertainty. "Miss Pie. Outside." She tucked her cello bow aside and began walking past towards the door. "Now."

Pinkie Pie plodded outdoors, followed by the musician pony. She plopped down on the ground in a puddle. “I really screwed the pooch, didn’t I?”

“At least this time you managed to stop yourself before you ended the party.”

Pinkie laughed weakly. “Yeah… at least this time I was only a minor screwup.”

Octavia drew a quiet and long breath. "Miss Pinkamena Diane Pie, your heart is in the right place. You are, in fact, a well known hero. However, none of that excuses your behavior. You do not understand nobility." She sat up on her hind-legs, her forelegs crossed. "I'm not one of them, mind. I just work for them. You come on too strong, turn them off, and then everyone gets angry. I've seen this before." She hiked a brow. "I live with someone that does that too."

“I’m sorry…”

“I don’t think I’m the pony you need to be apologizing to.”

“Oh my gosh, I came in to Sublime’s party and I called it boring. She must be so mad right now.” She started to head inside but a cultured hoof thrust in the way.

"No. You will let them be. Let things calm down and get back to normal. Tomorrow, at the very earliest, you can write an apology letter." Octavia's voice was steely stern, but there was a gentle expression on her face. "Don't chase this to the end, not right now."

Pinkie Pie pronked around the room, bouncing and putting the last of the streamers on the walls. Everything had to be just right. She could accept nothing less. She hopped over to Twilight, who had a checklist. “How’re we looking Twilight?”

“Streamers, check, confetti, check, balloons, check, party games, check and check, looks like everything is here looking like a prime Pinkie party!”

Pinkie Pie bounced up and down. “Perfect! That’s exactly what we need right now.” She sat down at the table. “I am pooped.”

“I know you want this to be great, Pinkie, but you really ran yourself ragged for this.”

“I know… I just… it needs to be perfect, because…”

She was cut off by the door to the Sugarcube Corner opening, and in stepped Sublime Soirée, only instead of dressing sublimely she was dressed more practically, with a simple but pretty blouse. “Is this the right place?” In behind her stepped Octavia.

Pinkie lit up. “You came! I wasn’t sure if you would come but you came! This is the bestest day ever!” She hopped up and pulled a cord from the top, and with a bang streamers and confetti rained down on the other pony, and a banner unfurled, reading in big bold letters:

“I’m sorry!” There was a happy smiling Pinkie Pie face on the banner.

Sublime smiled somewhat subduedly and stepped in for the party. “So this is how… ponies throw parties here in Ponyville?”

Pinkie bounced in besides her. “Yepper depper! This here is an official Pinkie party, just for you!”

“I’m flattered… I suppose.”

Pinkie pulled her along, and the party began in earnest. Party games were played and ponies generally had a good time. Including Sublime herself.

After a particularly dizzying game of pin the tail on the pony, Pinkie and Sublime sat down, watching the other ponies continue to play the game, laughing and playing.

“... I’m sorry, for how I acted about your party, Sublime.”

Sublime let out a big sigh. “I suppose it’s just as much my fault. Instead of being frank with you that it was a closed party, I tried to be clever and just be mean to you. It was unbecoming of me, and you did not deserve that.”

“Oh… I hadn’t… even thought of that.”

The two of them sat in silence, both watching the party again.

Sublime broke the silence this time. “Did you mean it, when you said you came to my party to see what sort of parties I threw?”

Pinkie's folded ears perked up in a flash. "Oh, yeah! I mean, who hasn't heard of Canterlot parties? And I heard you were the best.. But, you know, I… just didn't get it." Her hooves tapped on one another slowly. "I didn't like it, a party I didn't get…"

Sublime sighed. “And you decided to come see for yourself, did you?”

“Yupper doodle.” Pinkie put her head in her hooves. “I thought I’d just… easy peasy crash the party, and see what it was like.” She hung her head. “I’m sorry.”

Sublime stood up, straightening her blouse, smoothing it out. “Alright then.” She produced a small book and held it in her magic towards Pinkie. "This is the book that inspired me, before I assembled my first assembly."

Pinkie reached out with trembling hooves. "For me?!" When Sublime nodded, Pinkie pulled it close. "Thank you!" She squeezed it tight and rocked in place.

"Aren't you going to read it?" asked Sublime with an arched brow.

"Oh, right." Pinkie let it fall away far enough to at least see the cover. "How to celebrate the finer things in life with grace." She perked one ear at it, then the other, alternating a moment. "I will read this right away!"

"Do that." Sublime set a hoof on Pinkie's shoulder. "And next time, reply to an RSVP. That's all you need to do, mmm?"

Author's Notes:

This was a Collab with Radicaldishonesty. He suggested a birthday collab, and this was my idea, and then we wrote it together and here it is. Enjoy!