Several years ago I started to helping out as a Game Master for scripting (SphereScript) on Czech&Slovak Ultima Online (UO) server Moria. It was just as I started college and after several years of playing on this server. One of things I did was a mini game called "The Sheep Game". It was inspired by custom map for Warcraft III where were two teams fighting in 2 arenas. Each arena started with 1 (aggresive) sheep in it and when players killed it two more spawned in the arena of opposite team. Players could also upgrade sheeps. Team that survived longer was a winning one. I implemented similar game into our UO server, except replaced sheeps with monsters and upgrades with different kinds of monsters. We managed to have few tournaments before server was closed last year (2013). I believe I can say it was a popular game among our players, probably because of winning valuable prices :).
Those players in the middle are spectators and they are actually invisible for playing (fighting) players. I was the one on that blue llama and the one recording these videos was server administrator.