Electrical issues can be frustratingly difficult, as you know. If the circuit isn't working just right, the electricity will take other paths and can cause strange things like you saw.

There can be strange behaviours even when the circuits are working as designed. As a kid, I remember my brothers and I sitting in my grandfather's Chrysler. We discovered that if we pressed the brake pedal and activated the left turn signal, we could turn on the radio and listen to it without needing the ignition key!