Shell Game

In the 1920s, American painter and eccentric Waldo Peirce gave a turtle to the concierge of the building in which he lived. She was delighted with the gift and took great care of her new pet, and she did not notice when Peirce secretly replaced it with a slightly larger turtle. This continued for some time, with Peirce sneaking successively larger turtles into her apartment while she praised her miraculous pet to the neighbors.

Then, after a suitable pause, he began using smaller turtles.