Twilight, flipping through a book, sighed deeply. Pinkie popped up next to the chair where she was reading. "What's wrong, Twilight?"

"Gah!" Twilight shouted, reflexively flinging the book across the room. "Pinkie? Where did you come from?"

"I mean, there shouldn't be anything wrong," Pinkie continued obliviously, pulling a piece of paper out of absolutely nowhere and scanning it. "According to my calculations, the emotional high from saving the Pillars, and Stygian too, should keep up for at least another week! But you're sighing!" She leaned over and shook Twilight. "WHY ARE YOU SIGHING?"

Twilight pushed Pinkie away with her magic, giving herself a little breathing room. "It's actually about the Pillars. Remember in Starlight's old village, when she said the staff was one of the nine enchanted items of Mage Meadowbrook?"

"Only there were actually eight and her staff was a fake? Yeah! I remember!"

"Well, all my books said Mage Meadowbrook was an eastern unicorn, but she's an earth pony, lives in a swamp, and makes potions, not enchanted items! It just doesn't add up." Twilight gestured to a massive stack of books on the table beside her. "I'm trying to research it, but I just can't seem to make it fit. Every book on legends says Meadowbrook is a southern earth pony healer. Every book on magical items says she's an eastern unicorn enchanter. It just doesn't make sense!"

"Hmm... can I look at those?"

Twilight shrugged and pulled up a second chair. "Sure, Pinkie. But I doubt you'll figure it out either. I've been looking this stuff up for hours!"

Pinkie hopped into the chair and grabbed three books. "If it makes you stop sighing and get back on that emotional high, it's worth it!"

Twilight couldn't help but smile. "Pinkie, I swear, you'd do anything to make your friends happy!"

Pinkie gasped. "You're smiling! It's working!" She started flipping through books frantically, determined to keep that smile on Twilight's face.

As Twilight watched in amazement, she grabbed two more books, flipping through them in a storm of paper, checking one, then another. "Uh-huh... that makes sense... but then..." She added three more books to this whirlwind, and Twilight's mouth dropped.

It wasn't as if she hadn't done similar things, she reflected. It was just that she had magic, and thus could hold all the books up as she flipped through them all. Pinkie was keeping up this storm of research with just two hooves. And occasionally, Twilight realized, her tail as well.

"But what about..." Pinkie muttered, grabbing another book--that made nine, and she showed no signs of stopping. "Okay... so then... but that would mean..."

"Would mean what?" Twilight finally asked.

Pinkie Pie looked up. "It all makes sense! I can't believe I didn't see it sooner!"

"What makes sense?"

"It explains everything!"

"WHAT EXPLAINS EVERYTHING?" Twilight shouted, at the end of her patience.

Pinkie Pie bounced up and down on the chair. "They're two different ponies!"

"...What?"

Pinkie took a deep breath. "You see, one of your books of legends also included Mistmane and in a little teeny-tiny note at the bottom it told about how she went on all these adventures with this group of ponies and when she came home she'd create these beautiful presentations of everything that had happened to them kinda like shadow puppets only not and then her friend Sable Spirit had this one pony that was always her favorite from the stories so she named her kid after her and in another book it said Mage Meadowbrook's mom was named Sable Spirit and so obviously Mage Meadowbrook the enchantress unicorn was named for just plain Meadowbrook the earth pony healer!"

Twilight blinked several times.

"Pretty neat, huh?" Pinkie added.

"Um... yes?" Twilight said, still trying to process this. "So... just to clarify, you're saying that Mistmane's friend named her daughter Meadowbrook in honor of the other Meadowbrook, but they're not the same pony?"

"Exactly!" Pinkie exclaimed with a grin. "In fact, a third book said that Mage Meadowbrook had five siblings. They were probably all named after the Pillars too! We're lucky only one of them grew up to be a famous enchanter, or we'd have an even bigger problem on our hooves!"

And, leaving Twilight to contemplate that prospect in horror, she bounced out of the room.

Author's Note

Yeah. To say the two different presentations of Meadowbrook bugged me would be an understatement.
In "A Health of Information" Fluttershy says that the Mystical Mask is Mage Meadowbrook, but I'm ignoring that because I think she probably just assumed it was the same Meadowbrook that Twilight had mentioned back in Season 5, just like everypony else did.