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The Big Book 'O Rules is the official school rulebook for Jerome Horwitz Elementary School written by Mr. Krupp. It only made a physical appearance in the book Captain Underpants and the Wrath of the Wicked Wedgie Woman.

There are two known rules in the book:

  • Rule 411: Don't kick school property into outer space.
  • Rule 7,734: Don't transform into big, flying robots during afternoon recess

TV Series[]

It also makes an appearance in The Epic Tales of Captain Underpants. In that iteration, however, it is shown that Mr. Krupp did not write the book, and has in fact been writing down his own rules in it to get George and Harold in trouble. Thus, in, The Sickening Fumes of Smartsy Fartsy and The Troublesome Treachery of the Thieving Toot Fairy, George and Harold attempt to steal it so they can bring it to Dr. Vil Endenemys so he can fire Krupp. In The Tenuous Takedown of the Tyrannical Teachertrons, Grace Wain mentions that Mr. Krupp's rules aren't to be considered official until George and Harold's expulsion is repealed. Given that the expulsion is repealed, it can be assumed that this made these handwritten rules official rules.