Army-Navy game. The pre-game on field "Prisoner Exchange".

Hilariously clever - "the prisoner exchange" West Point and Annapolis have been doing a 1 semester exchange program for the last few years so young officers are aware of the other branch's structure, tactics, lingo, etc.

Before the game ON THE FIELD they exchange these prisoners so they can root with their fellow students. They are given back after the game for the bus rides home.

http://www.usma.edu/news/SitePages/Cadets,%20midshipmen%20will%20participate%20in%20traditional%20exchange%20at%20Army-Navy%20Game.aspx