Gala Contemplating… by Salvador Dali

This effect is also used to generate these images http://cvcl.mit.edu/hybrid_gallery/stein_series.html

From the page "In the eight hybrids arranged above, at a close proximity, you will perceive Albert Einstein. Each image carries a shadow of an ulterior individual as well. Stepping away from the images will reveal eight respective identities of notable figures that exist in the low spatial frequency of the images, and Einstein will slowly disappear. Each hybrid carries a dichotomy of fame arisen from diverse disciplines, and a legendary cognitive intellect. The conversion of which gives rise to unique personalities."