"To create awareness at point-of-purchase, we rigged everyday shopping trolleys with motors, thereby creating and arsenal of "ghost trolleys". The trolleys were then filled with ghost pops and driven by remote controls from hidden locations. They moved around supermarkets by themselves prompting shoppers to take a pack while getting quite a few interesting reactions." -- Network#BBDO, Loerie Awards 2005, Gold for Ambient/Outdoor
Also, check out how Yamaha turned shopping carts into motorbikes.