In the kitchens at Sugarcube Corner:

“Crescent, Crescent bo-bescent

Banana-fanna fo-fescent

Mi my mo-mescent

Crescent!” sang Pinkie.

“Pinkie, Pinkie bo-binkie

Banana-fanna fo-finkie

Mi my mo-minkie

Pinkie!” sang Luna.

“Applejack, Applejack bo-buh-blapple-ack! Ow! I think I thprained my tongue!”

“Heeheehee!”

Pinkie Pie was putting the finishing touches on a tray of cupcakes while Luna worked on the invitations.

“All right,” announced Luna. “The next one’s ready to go!”

“Do it!” cried Pinkie.

Luna focused on the scroll in front of her, concentrating. Her horn flashed. The scroll burst and vanished.

“It’s on it’s way!” she said.

In the family room of Sweet Apple Acres:

Applejack burped.

“Better out than in, dearie,” said Granny Smith sweetly, looking up from her knitting.

“Ay-yup,” agreed Big Macintosh.

"Uncouth," giggled Apple Bloom.

“Whut in tarnation?” exclaimed Applejack. A scroll had appeared in the air in front of her. The scroll floated softly to the floor of the family room and unrolled.

Huh, thought Applejack. Don’t reckon I know this Crescent Cookie, but if she’s a friend of Pinkie Pie, she must be okay.

I guess Twilight must be behind this stunt with the invitations. That girl, I swear. She’s a caution.

Wull… it’s summer. Days are long and nights short. Why not?

Grabbing a pencil in her mouth, she wrote, I’m in on the scroll.

Now eat the scroll? All right. Huh, tastes like watermelon. Not too bad.

Better get my hat.

In the kitchens at Sugarcube Corner:

Applejack’s RSVP popped into the air in front of Luna.

“Yes! Yes! Yes!” Luna hopped around wildly, clutching Applejack’s reply to her chest. “Applejack said yes! She’s coming. Everyone is coming!”

“Woot! Woot! Woot! Wave the finger, Crescent! Wave it!” cried Pinkie.

Luna accepted the We’re Number 1! finger and waved it, feeling completely ridiculous. Still, she felt very happy and very relieved as well.

“So, that’s it, then,” Luna said. “We have everyone. Twilight Sparkle…”

“And Spike!” added Pinkie.

“And Spike,” agreed Luna. “Applejack. Rarity. Rainbow Dash. Fluttershy.”

“And Gummy!” added Pinkie, hugging the tiny reptile to her bosom.

“And Gummy,” concluded Luna. “That’s quite a guest list.”

“Don’t forget our Special Surprise Guest: Princess Luna!” said Pinkie.

Luna grinned. She consulted her clipboard once more. “I’m glad that Twilight Sparkle agreed to let us hold the party at the Library. I wouldn’t want to disturb Mr and Mrs Cake any more than I have already.”

As she checked the names off of her list she thought, with some smug satisfaction, So much for you, Captain Bucephalus! I’m going to throw a party and make friends and there’s nothing you can do to stop me!

“BWA-HA-HA-HA-HA!” chortled Luna, giving her black moustache a twirl.

“Oooh, that sounded spoo-oo-ooky, Crescent!” squeaked Pinkie.

“Ah. Did I do that out loud? So sorry.”

Ever since her last meeting with Captain Bucephalus, Luna had been nursing a small spark of resentment against her self-proclaimed guardian. Luna had enjoyed baking cupcakes, writing invitations and planning games, but her pleasure had been spiced, just a little, with sweet revenge. With each cupcake iced and balloon inflated, there had been a gleeful and growing ember of spite: Ha! Take that! And that! How do you like that, Captain Bucephalus?

Luna completed her review of the guest list. “I can’t thank you enough for your help, Pinkie,” she said. “I couldn’t have thrown this party by myself. You have so many good friends. I have no friends of my own to invite,” she finished, sadly.

“Don’t you know anyone?” Pinkie Pie asked.

“Only my sister, and she’s far too busy to attend a small function like this,” said Luna. “Oh, I’ve been introduced to a round of ministers and government officials, courtiers and distant relatives. I can’t remember half their names. But for the last week, it’s just been them, my sister… and that idiot Captain Bucephalus, ‘Commander of the Lunar Guard.’” Air-quotes.

“Well,” suggested Pinkie, brightly. “Why don’t you invite him?”

“Invite Captain Bucephalus? My supposed ‘protector?’” Air-quotes. “Are you crazy? He’s the one that kept me trapped in the Lunar Tower! He’s the one who has been driving everypony away! He’s why I’m still alone!”

Luna seemed to swell with rage. In the corners of the kitchen, the shadows grew.

“In a thousand years nothing has changed! No one visits! No one cares! And it’s all his fault!”

“Golly,” said Pinkie, saucer-eyed. “He must be a real Meanie McMeaniepants! How did you finally manage to escape from the tower?”

“I— well, I just left,” said Luna, confused.

“Didn’t he try to stop you?” asked Pinkie. “I bet you had to fight him off. Hi-yahh!” Pinkie drew herself up into a fighting crane stance and promptly fell over.

“Well, no,” admitted Luna. “But he tried to follow me! To protect me, he said,” Luna sneered. “So that he could stop anyone from getting near me, he should have said.” Pinkie’s questions were starting to vex her. Why are you arguing with me? Why can’t you just be angry, too?

“Huh,” said Pinkie, getting up. “Did you ever ask him not to do that?”

“Ask him not to—? What?”

(“I’ve been here in the tower for more than a week now, and we’ve hardly talked.”)

“I, I never said so, not in so many words, but, but it was his responsibility…”

(“Who’s the Princess here?”)

Luna stopped.

No. Oh, no.

It was my responsibility, wasn’t it? It was always my responsibility. To leave the tower. To go out. To make friends.

In a thousand years, I’m the one who hasn’t changed. I held myself, high and aloof in my beautiful sky, and waited for my admirers to approach me, to worship me. When did I ever reach down to them?

When did I even try throwing them a party?

The carefully nurtured flame of resentment that she had held in her heart finally snuffed out, leaving behind only the soot of remorse.

“Oh, Pinkie,” Luna began, green eyes brimming.

“I’ve been a terrible, terrible Princess. In truth, it wasn’t Captain Bucephalus’s fault. It was all mine.”

(Honesty…)

“All along he was only doing what he thought was best to help me, to care for me, but I repaid him with anger and ridicule. Poor Captain Bucephalus!”

(...kindness...)

“He has given me his unselfish devotion for years, even when I was no more than the Mare in the Moon. How can I show him any less in return?”

(…loyalty…)

“I must do something for him. Something special. For his sake and not for mine!”

(…generosity…)

Through her tears, Luna suddenly discovered a smile. “Oh, I know! I know what to do! It’s so obvious! Ha ha ha! Pinkie Pie! Will you help me, please?”

(…laughter…)

“Of course I’ll help you!” exclaimed Pinkie.

Luna brushed her tears away. “Thank you. Thank you so much. You are a good friend.

“Now, we have a lot of work to do. Can you show me how to make party decorations?”

(…magic!)