The iconic yellow smiley face, found in popular culture is known among many of the alien cultures of the galaxy as "The Smiling Human".  

Different cultures perceive it differently, but it is nearly always associated with humans.  In some cultures it is a symbol of restraint, because it shows the mouth drawn back in a smile, but without bared teeth.  Some see it as symbolic of a disingenuous attitude or sarcasm.  The most popular interpretation is to see it as emblematic of cleverness and good fortune, since humans are the most technically advanced species, and the face has to be smiling about something. 

It is widely recognized and popular enough that that there is a good bit of interstellar commerce attached to it.

"The Smiling Human"  was also the name of a popular saloon/casino on New Albuquerque that became a galaxy-wide chain during Era-2.