Why do peole say "let's hang out" and complain that they have not seen you / But never call, make plans, or go out when invited?
A Jackie Chan meme.
Jackie Chan is the martial arts actor holding his hands to his head in disbelief. The picture, known as "My Brain Is Full Of F...", stands for total bewilderment. Captions describe things that make no sense - a confusing plot, a math problem, a relative's logic. It's the meme for being baffled.