Philips impossible object ads

These impossible objects were popular a couple of decades ago though the ideas had been around for years through the graphic of Dutch artist MC Escher and Swedish Oscar Reutersvard who designed these ads for Philips.  I found the five in The Economist magazine during 1986, each was part of a spread with the right-hand page singing the praises of  the companies problem solving capability.  
     The clever little Lego piece was probably Photoshopped.  Google impossible objects to see plenty more.