The self-proclaimed 'art terrorist' Banksy made headlines back in March for sneaking his own work into various New York art galleries. Now he's done it again. He managed to sneak some faux prehistoric rock art into the British Museum. The rock art depicted a caveman pushing a shopping trolley. It hung in the British Museum for two days before being detected. The British Museum has now loaned the rock art back to Banksy who is displaying it at his own show in London. But they expect to get it back eventually.