May be performed with just the scrotum and testicles, or with the scrotum tucked over the penis and then pulled tight. Sometimes accompanied by shouts of "alien brains" or simply "blaaaah."
Generally used as a sign of disrespect or in an attempt to disgust (sim. moon). As with similar acts, the term "alien brains" can refer to both the act of presenting alien brains, or the rearranged genetalia themselves.
Kristina looked sick, so I showed her some alien brains. She barfed everywhere.