That evening, after completing her rounds and the preliminary sorting for the day after the Summer Sun Celebration, Derpy dropped Dinky off with Mrs. Cake for the evening, and trotted quickly down the street towards the Library.
She was just in time. In the distance she could see a lavender pony she didn't recognize coming up the street from Fluttershy's meadow, with Fluttershy herself right behind her. There was a small dragon sitting on the lavender pony's back, and he and Fluttershy were chatting amiably.
The lavender pony, on the other hoof, was looking tired, bored, and seriously aggrieved by the whole thing.
Derpy nodded. If any pony needed the Pinkie Pie treatment, this one did!
She slipped into the darkened main room of the Library and shut the door. To avoid any catastrophes she carefully allowed herself to be buffeted back into the crowd waiting in tense, happy silence within.
There was a long wait, and then she heard voices outside. The door was flung open, and Fluttershy flitted in, carrying the dragon. The lavender pony shot in after her and nabbed her by the tail, causing the dragon to fall to the floor. She quickly bundled Fluttershy back outside.
"Yes, yes... we'll get right on that! Well... G'night!"
SLAM. She shut the door. And heaved a sigh of relief.
"Huh! Rude much?" The dragon grumbled from the middle of the darkened room as she trotted forward to join him.
"Sorry, Spike! But I have to find proof to convince the Princess that Nightmare Moon is coming, and we're running out of time! I just need to be alone for a while so I can study without a bunch of ca-ra-zy ponies trying to make friends all the time! Now, where's the lights?"
It was one of those perfect straight lines that a large crowd standing in a darkened room will wait endlessly for, no matter what happens or is said.
The lights flicked on.
"SURPRISE!"
Derpy looked around. Pinkie had outdone herself, yet again. The room was decorated with streamers and balloons. There was a snack table with drinks, and several of the ponies had noisemakers, which they plied with wild abandon. And just as the lights went on, Pinkie had touched off her party cannon, filling the air with confetti.
The lavender pony just stood there, stunned by it all.
Pinkie ran up to her.
"Surprise! Hi! I'm Pinkie Pie! And I threw this party just for you! Were you surprised? Were ya? Huh? Huh? Were ya? Huh-huh-huh?"
"Very surprised!" The pony agreed with her. "You see, libraries are supposed to be quiet!"
"Ha-ha-ha! That's silly! What kind of a welcome party would this be if it were QUIET? I mean DUH! BO-RINGGG!"
Derpy smiled as she watched Pinkie Pie follow the new pony over to the drinks table, nattering away at high speed. The new pony tried to ignore Pinkie's blather, while distractedly pouring herself a drink from a random bottle on the table.
Derpy saw all her friends gathering in a group behind Pinkie: Applejack, Rarity, Rainbow Dash, and Fluttershy as well, getting ready for their cue.
Then the new pony took a big sip of her drink.
"And now you have LOTS and LOTS of FRIENDS!" Pinkie cried.
The lavender pony turned towards them, her face contorting in surprise, shock, horror, and various degrees of eye-watering pain.
"Are you all raight, sugarcube?" Applejack asked, concerned.
"Awwwwww," Pinky said. "She's so happy she's CRY-ING!"
What happened next was amazing. Derpy had never seen a pony leap in the air, her mane and tail bursting into flames, snorting like a train whistle. Then, looking severely singed, the lavender pony shot out of the room through the rear door.
Her dragon picked up the bottle she'd poured from. His eyes went wide. "Hot sauce!"
Pinkie Pie's hoof reached out and tipped the bottle in his claw, pouring a large dollop of sauce onto a nearby cupcake. Which she then tossed in the air and ate, with every sign of enjoyment.
"Yum," she said indistinctly, while the others stared at her in mixed horror and amazement, "This is GOOD!"
Applejack sighed. "Uh... wayall, all in all, that didn't go quite how we expected!"
The dragon trotted over. "You just gotta give Twilight some time. She's been so focused on this, uh... research project of hers that she hasn't been able to unwind all day!"
"If'n you say so, Spike! Oh, and by the by, this here's Derpy, our mail-mare," she added as Derpy trotted over to join them.
"Hi, Derpy! Hey, I like your eyes!" Spike said, "They're cool!"
He said it so earnestly that Derpy couldn't help but smile. "Thanks, Spike! You got nice dragony eyes yourself!"
Spike preened happily at that.
"So, girls!" Rarity said. "Do we give Twilight a few minutes, and then go find her? Or... should we carry on and let her join us whenever she feels ready?"
"I'll just... go check on her, make sure she's okay." Spike scampered off after Twilight.
"Um," said Fluttershy guiltily. "We might have overdone it, actually!" Fluttershy whispered.
"Nah, she's just flighty!" Rainbow said. "Seen it before!"
"I dunno." Applejack shook her head. "Maybe we are bein' kinda pushy here. This is her place, while she's here. Maybe we should give her some space until she gets to know us."
Derpy tried to imagine what it would be like, coming home to the room above Quills and Sofas after a long hard day of posting letters, one after the other, in the same slots in the same front doors every single day, and finding the room redecorated in party favors, with all her friends there, and not having to worry about doing a single thing to keep it all going.
It would be the best thing in the world, ever.
"Maybe... we should just keep her party going?" she ventured.
"Even if she don't come back?" Applejack asked, doubtful.
"Especially if she doesn't, dahling," Rarity said. "So she knows we're here for her, whenever she needs us!"
Applejack thought about it, then nodded. "Pinkie, think ya'll can keep the party stoked all night?"
"Are you CRAZY? I can keep a party stoked all YEAR!"
- - - - - - - - - - - - - - -
The party roared on into the wee hours. But Derpy had to beg off early to go collect Dinky from Mrs. Cake, read with her in bed, and then tuck her in.
Afterward, she carefully climbed out through their window and steadily flap, flap, flapped her way up onto the roof. She sat down and watched the Moon with its Mare shadow, hanging in the sky.
She sent her wishes to the Mare, and didn't much mind nothing happening. It was nice just having someone to ask.
Then she tilted her head, puzzled, staring at the sky.
Was she imagining it, or were the Shepherd Stars moving, ever so slightly? Getting closer to the Moon?
She shook her head.
Derpy, you are so tired, you're seeing stuff.
And went to bed.