Escher sometimes combined two and three dimensional images into a single print, like his piece " Reptiles." In this peace is looks as if the reptiles come to life out of the picture and walk around and then go back into the two dimensional picture.
Escher had many great quotes. Such as, "So let us then try to climb the mountain, not by stepping on what is below us, but to pull us up at what is above us, for my part at the stars; amen - M.C. Escher"