1961 Clemson vs. South Carolina: South Carolina 21, Clemson 14

How the game went

In 1961, the USC fraternity Sigma Nu pulled what some have called the greatest prank in the rivalry’s history. A few minutes before Clemson football players entered the field for pre-game warm ups, a group of Sigma Nu fraternity members ran onto the field, jumping up and down and cheering in football uniforms that resembled the ones worn by the Tigers. This caused the Clemson band to start playing “Tiger Rag,” which was followed by the pranksters falling down as they attempted to do calisthenics. They would also do football drills where guys would drop passes and miss the ball when trying to kick it. Clemson fans quickly realized that they had been tricked, and some of them angrily ran onto the field. However, security restored order before any blows could be exchanged. The Carolina frat boys had also acquired a sickly cow they planned to bring out during halftime to be the “Clemson Homecoming Queen”, but the cow died en route to the stadium. Carolina won the game 21–14.

Source: Wikipedia