sneak up on an upright

Cow tipping is a http://en.wikipedia.org/wiki/Pastime supposedly practiced in http://en.wikipedia.org/wiki/Rural areas. It is often considered an http://en.wikipedia.org/wiki/Urban_legend^{http://en.wikipedia.org/wiki/Cow-tipping#_note-Debunk} as well an act of http://en.wikipedia.org/wiki/Animal_abuse.^{http://en.wikipedia.org/wiki/Cow-tipping#_note-floridaban} The act is theoretically performed by participants who sneak up on an upright, sleeping cow and push it over for amusement. There are factors which make success in this unlikely, and a variety of calculations have been applied to determine if cow tipping is physically possible, sometimes with humorous intention.^{http://en.wikipedia.org/wiki/Cow-tipping#_note-0http://en.wikipedia.org/wiki/Cow-tipping#_note-1}

In 2004, a legislator proposed a ban on "cruelty to bovines", which while not specific to cow tipping, included language that would apply to cow tipping: "A person who, for the purpose of practice, entertainment, or sport, intentionally fells, trips, or otherwise causes a cow to fall or lose its balance by means of roping, lassoing, dragging, or otherwise touching the tail of the cow commits a http://en.wikipedia.org/wiki/Misdemeanor of the first degree."

<sup>I understood the `sneak up on an upright' as (advanced stealthily with an erect position). But I wonder to whom this phrase refer to, i.e. the cow or the participants.

Also, I wonder how we can push the sleeping cow over?

Please help me.</sup>