Prank Art.

Brilliant.

From the AP:

LONDON -- This image released by the British Museum shows a hoax cave painting of a primitive man pushing a supermarket trolley which was on display in the British Museum. The work was planted by an anonymous "art terrorist" called Banksy and museum staff were made aware of it after he put a message on his website, saying that the 10in by 6in rock "had remained in the collection for quite some time." This is not the first time Banksy has stuck fake objects to gallery walls and waited to see how long it takes before curators notice. (05/23/05 AP Photo/British Museum/HO)