The Looney Tunes universe had boundaries as severe as an Acme anvil to the head.

A list of rules for the creators of the Wile E. Coyote and Road Runner cartoons has been circulating online and the instructions explain why every episode was almost exactly the same.

Rules for the show include a restriction on dialogue (save for “Beep-beep!”), setting (“All action must be confined to the natural environment of the two characters — the Southwest American desert”) and outcomes (“The coyote is always more humiliated than harmed by his failures”). There’s even an instruction on who the real enemy of Wile E. is: “gravity.”

The list comes from the autobiography of former Looney Tunes animation director Chuck Jones, Chuck Amuck: The Life and Times of an Animated Cartoonist (1999). Director Amos Posner posted the list to Twitter on Mar. 4, saying, “Still obsessed with Chuck Jones’ coyote/roadrunner rules. Awesome to so clearly, concisely define your characters.”

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