The idea likely took off from a half-understood bit of science: that your favorite souvenirs were creating a magnetic field that was somehow interfering with the fridge's internal sensors or compressor. That the magnets could, in theory, be "confusing" the refrigerator into working harder to maintain its temperature. In reality, though, the magnets on the outside of your fridge are far too weak to penetrate the insulated door or affect the circuits inside.