On June 26, 1944, with more than 50,000 in the stands at the Polo Grounds in New York, the Dodgers, Giants, and Yankees played in the first and only three sided game in the history of Major League Baseball. The concept was to have all three New York teams play each other in an exhibition game to raise money for War Bonds, the teams would play a round robin of sorts that had one team sitting out an inning then appearing in two consecutive innings before sitting out again, the game was played a regulation nine innings with each team playing a total of 6 innings apiece. Sounds crazy don't it? That's because it is. The final score had the Dodgers coming out on top with a score of 5-1-0, the Yankees scored a run while the Giants were shutout. While the concept was an odd one it was a huge success as the crowd raised more than $6,000,000 to contribute to the war efforts.
If you would like to read more about this game check this out: http://research.sabr.org/journals/three-dimensional-baseball