Ive attached pictures below, the piston is magically powered by nothing. I've made a 1 tick T Flip Flop, the end of which is the redstone block above the magically powered piston. Using the T Flip Flop as an on/off switch for my redstone door. However, building the T Flip Flop and placing the piston for the door permanently powers the piston with 0 input from the player. 

I suspect because its a 1 tick T Flip Flop the game is pre-emptively powering the piston in anticipation of the 1 tick switch.

Quitting and reloading the world fixes this temporarily, but upon rebuilding the 1 tick T Flip Flop, the piston will immediately re-power itself, despite no physical connection to any redstone.

I've also attached an image of the T Flip Flop i built, the key difference being the rightmost piston is facing downwards, with a redstone block on the end.