I grew up in the Midwest. The version of cow tipping that I heard about was to get some naieve urbanites, typically college students, all geared up about cow tipping and the theory behind it. Then take them to a pasture in the middle of the night, typically with alcohol involved. The idea is that they will return to the dorm rather covered in mud or "mud," as it were, never quite sure if they were pranked or not.
Of course I have no idea if anything like this has ever actually happened.
