The main Idea for the plungers, and with Plünge was for a carbon copy challenge of Alt.Ctrl.GDC design wise, for this challenge I was tasked with making our controllers as I had the most experience with minor electronics and wood working. For the challenge there were two different ways for the teams to actually make their controllers, the first way was to make a physical object and have the game supplement the object and have most of the focus be placed in the real space rather than that he virtual one, the second was to have you game be controlled by the most literal interpretation of the games movement system IE (A game about sledding down a hill be controlled by leaning on an actual sled).
We opted for a mixture of the two in which the controller defined the game but the main focus for the player is the game itself, as for the origins of the idea, we decided that we wanted to make a game with something that would get a laugh out of anyone who played with it, as such a toilet plunger was brought up and we went with the idea.