I remember, back in the '60s, ads in TV Guide for plug in TV antenna adapters. A power plug with a sideways cylinder (looked like made of plastic) mounted to the plug, and twin lead going into that cylinder. I would guess a pair of high voltage capacitors connected to the power line and twinlead conductors. Making the house wire act like more twinlead, eventually getting TV signals from the overhead power company service wires, at least in theory...
No noise immunity or ghost suppression you'd have with a real rooftop antenna.