My dad was a produce manager years ago and a customer insisted he only wanted red grapefruit because they are sweeter.
Dad told him there is no difference and made a bet that he couldn’t tell them apart. He took the customer in the back, blindfolded him and fed him slices of grapefruit, while the customer said “that one’s white, that one’s red”.
Dad took off the blindfold and showed the guy he had only fed him the white, so the customer said I guess you were right.
Dad being a character, he then pointed to the corner and said “Not only that, but YOU”RE ON CANDID CAMERA!” The customer went nuts reacting to the (nonexistent) tv camera.