NinjaNomicon

The NinjaNomicon, or simply Nomicon, is an 800 year-old book that teaches the Norrisville Ninja wisdom and skills.

About the Nomicon
Randy Cunningham gets his hands on the book and using what he learns from it, he helps keep the world safe from the forces of evil. Whenever Randy or any Ninja is in need of help or information about something, he can just ask the Nomicon. To answer his question, the Nomicon communicates mentally, leaving his or their physical body in a trance-like state. There's a running gag that whenever Randy goes into the Nomicon, Randy will often fall to the ground and sometimes have the Nomicon hit his head.

The Nomicon may have a mind of its own. In "The Tale of the Golden Doctor's Note", when Randy "dissed" it, the book glowed and gave off a roar-like sound. And in "Viva El Nomicon", when Randy was acting too confident in himself, the Nomicon locked up until he learned the lesson. It also spoke to Mac Antfee as shown in a flashback to Randy in "Ninja Camp".

The Nomicon may also have the power of Precognition. This is proven that the book seems to know in advance what kind of situation Randy is about to get into, and gives lessons which act as either warning and/or advice for that exact situation. For example, in "Stanks Like Teen Spirit", it warned Randy beforehand that his enemies were up to something, but Randy didn't take it to heart, and because of it, he woke up to find a lot of stanked monsters.

The Nomicon can also only be opened by the one who is chosen to be the Ninja. This was demonstrated in "Raiders of the Lost Nomicon", when Viceroy, McFist and even the Sorcerer attempted to open it with no success, although it's implied the Sorcerer's magic of red stank would have succeeded if Randy hadn't interfered. Howard failed to open it as well in "The Ninja Identity". However, it seems it can choose who can and cannot open it. Bucky Hensletter opened it in "Raiders of the Lost Nomicon" since he claimed it had "Non-school board approved ideas in it", and it also refused to open for Randy in "Viva El Nomicon".

In "Shloomp! There It Is!", Once Howard notices that somethings up wish Randy (who is actually NomiRandy) to get into the Nomicon. He can't until he throws it at a garbage box and it flies back at him, open, so he can get in, freeing the real Randy. Randy then goes to defeat NomiRandy in Howard's body, before returning things to normal.

While it often leads Randy to the pages where it feels Randy needs to go, the NinjaNomicon doesn't seem to have the ability to deny him when Randy is particularly determined. He has on several occasions forced his way into the House of Forbidden Knowledge and taken the ultimate lesson too early.

It's revealed in "The Ninja Supremacy", upon the Ninja's time ending, they take the Ultimate Lesson, whereupon their minds are wiped and the Nomicon absorbs all their experiences so it can be passed on to the next Ninja.

Trivia

 * The NinjaNomicon's name may be inspired by the Necronomicon.