red notebook 

it means duh. something as obvius as a bright red notebook

when im trying to eat?? duh, red notebook!

red notebook by MrSquiggles November 27, 2011

Red Notebook 

The wretched notebook that ruined many friendships due to a single slanderous note about an innocent individual. Often associated with timbits, volleyball games, and pizza sharing. It’s a curse to read anyone’s personal diary, as it may include lies about you…

“The red notebook curse is real! You must never read anyone’s diary. It may come with many hardships and false opinions of you or others.”

“I’m tempted to read that red notebook, I’ve seen the owner write that they hate me multiple times, I’m curious but I shouldn’t. It may make me despaired.”

Red Notebook by Ethan Tang stan (NOT Ethan) April 24, 2023

red notebook! 

"Red notebook!" is an exclamatory approximately equal to the meaning, "that is so obviously obvious and apparent that you must be an absolute moron not to have caught it."

In other words, DUH. Red notebook!

Usually accompanied by rolling eyes or, in text or IM conversations, an eye-rolling emote.

"Omg you mean all that music I downloaded from Pirate Bay was pirated?!"
"Duh! Red notebook!"

OR

"Hey, where's Allie?"
"I'm right here. Red notebook!"

red notebook! by SharkyFishEaterVegetarian August 19, 2009