The term “you don’t say” is a colloquial expression to suggest surprise or bewilderment in response to a statement. Additionally, the phrase may also be used as sarcasm to something obvious (and yet still stated). This latter definition was appropriated to a contour drawing of Nicholas Cage and together formed the You Don’t Say meme.
The image of the Academy Award-winning American actor originated from a scene in Vampire’s Kiss, a 1989 dark comedy/psychological horror film about a publishing agent’s gradual submission into madness after persuading himself that he is becoming a vampire. In the scene where the image of Nick was taken, his character Peter Leow anguishes his secretary.
Before the meme surfaced, the Nick Cage’s reaction face was used in a demotivational image uploaded to Roflrazzi in August 2009:
Two years later, the contour drawing appeared on Reddit.
As a side note, the meme is similar to the O RLY image macros. This image of an owl is popularly used in Internet forums to sarcastically respond to obvious statements, along with ones that are predictable or blatantly false.
Best of You Don’t Say Meme