Greys are the alien that is drawn up by the slowest kid in class during the "draw what an alien would look like" art project day. And then everyone in the class laughs at it, and the teacher gets pissed gives him an F and writes the F in big red sharpie on his forehead because that's how much she was done dealing with this kid and his shit, and then she goes home and has to drink herself into a stupor because she fucking hates dealing with all these dimwitted kids who steal her meaning for life away due to how utterly fathomless and unbearably dim they are in every way and expression of being and then she puts on some fleetwood mac, fists her vagina until competition and boom, she passes out immediately afterwards.

basically grey alien would be the "visualized average representation" of what an alien would look like according to all of humanity. the averaged out representation would come out looking like a grey alien. a fucking stick figure from outer space. goddamnit, humanity is dumb AF lmao