This is going to be a place for random short pieces, not associated with any particular timeline of mine.

First up: The Care and Feeding of Isabella Garcia-Shapiro, from a discussion with Sabrina06.

Isabella stormed into the boys' bedroom, waving the book at Ferb as Phineas chased after her, trying to convince her to stop.

"What is the meaning of this, Ferb?" Isabella shouted.

Ferb looked up from his position on the bed. Two days earlier than I expected. Interesting. "I should think that's obvious."

"Did you write this?" she asked, as Phineas stood behind her, unsuccessfully trying to reclaim the book.

"What does the cover say?" Ferb asked.

With a glare, Isabella read the cover aloud. "The Care and Feeding of Isabella Garcia-Shapiro."

Ferb shrugged. "Phineas asked for advice on your relationship. I figured it was easier to write it all down at once."

"How did you know all this? How did you know my favorite cake is red velvet? Or that I love it when I get kissed on...never mind." Isabella blushed.

"Observation," Ferb said.

"You can't have gotten everything from observation," Isabella said. "It's impossible for you to know everything about me. The book can't have everything."

"Pick a number between 200 and 300," Ferb said.

Isabella glowered at him, and said, "273."

Ferb grinned. "Turn to that page and read it."

Isabella flipped through the book. "Here we go. Page 273." She cleared her throat and started to read. "Eventually, Isabella will learn about this book and insist on seeing it, and because you are incapable of denying her anything, you'll show it to her. She'll get upset and say it's impossible for the book to know everything about her. Ask her to pick a number..." She trailed off, reading down the page, her eyes wide.

"Keep reading," Ferb said. Phineas, looking over her shoulder, started laughing.

Isabella sighed. "Ask her to pick a number between 200 and 300. She'll pick 273. Then tell her to turn to that page and read it."

Ferb put his hands behind his head and smiled at her as she flipped through the rest of the book.

"Hey, the pages after that are blank. What's up? Ran out of things to say?" Isabella asked.

Ferb shook his head. "Go to page 274."

Phineas reached over and flipped back a few pages. Isabella read it out loud. "This book is accurate as of the time of writing. Your relationship with Isabella will change as you two grow up together, so you'll need to update it on the following pages. I've given you a start. Now go write the book of your relationship together."

Phineas plucked the book from her fingers and tossed it on his bed, then took her hand and led her out of the room.