Logistics company DHL pulled a clever prank on its competitors and had them advertise for the company for free. The “Trojan Mailing” prank used large boxes that were painted with temperature-activated ink that turned black when exposed to sub-zero temperatures. DHL then hired its competitors like UPS and TNT to pick up these boxes to have them delivered to addresses that were difficult to find. Over time, the boxes eventually warmed up, revealing a hidden message on the front saying “DHL is faster”. The delivery person from the other companies had no choice but to deliver the ‘Trojan’ boxes, advertising the message to everyone who walked past them.
