The Rules of Road Runner vs. Wile E. Coyote

The Road Runner cannot harm the Coyote.
No outside force can harm the Coyote.
The Coyote can stop anytime he wants.
No spoken dialogue can be uttered ("beep beep" and cries of pain excepted).
The Road Runner must stay on the road.
All action must be confined to the natural environment of the two characters (southwest America).
All mechanical objects must be obtained from the Acme Corporation.
Gravity should be the Coyote's greatest enemy, whenever possible.
The Coyote should be more humiliated than harmed by his failure.
The audience's sympathy must always remain with the Coyote.

From "Chuck Amuck: The Life and Times Of An Animated Cartoonist"