Haha - yes we have been asked that question before!!
We are a five player league, but a few of our teams either have extra players, or players that are perhaps new to the game, or would benefit from extra games to improve. So, to encourage this we play a 6th game. It doesn't effect the score of the main league, but it has it's own little league with it's own trophy. If there is no extra players then the captain from the opposing team selects a player, usually the lowest scorer from their five. This has caused a few headaches this season though, and we now have two teams with only four players :):):):):)