I suffered from this once after a marathon session of Grand Theft Auto. My lawyers advise me against saying anything else.
The Tetris effect refers to the ability of any activity to which people devote sufficient time and attention to begin to dominate their thoughts, images, and dreams. It is named after the video game Tetris, in which users have to rotate different shapes as they fall down the computer screen to fit together in a neat pile at the bottom. People who play Tetris for a long stretch of time may be subsequently involuntarily prompted to think about ways different shapes in the real world can fit together, such as on seeing boxes on supermarket shelves. They may also see images of falling Tetris shapes in dark parts of the visual scene or when they close their eyes.