When I was a kid, our family's portable stereo had a bunch of weird radio bands on it, by which I mean anything other than AM and FM, the edges of some shortwave bands picked up the radio chatter of local fishermen here and there.

One time a friend and I stumbled into one of these conversations, the engine of some boat had stalled, my friend plugged in the headphones into the microphone jack and started to talk with the guy on the other end.
Of course he wasn't, but his improv and timing was impeccable, it really did seem like the setup was working as a transmitter also.

Decades later, I still clearly remember the way my friend mimicked an adult and technical conversation to a tee, promising to the stranded fishermen that backup was on the way... into the right earcup of a set of headphones.