University of Texas:
You have one cow. The Aggies steal it after winning a football game, and brand the cow with the score of the game. You get the cow back and then use a running iron to cover the 13-0 score with a made-up name for the cow, "Bevo".
Legend says this happened in 1916. Records differ.
http://en.wikipedia.org/wiki/Bevo_(mascot)
