Person 1: So......How did you know you were gay?
Person 2: I looked in the mirror and they were looking a little gay.
Person 1: So you had sassy balls?
Person 2: Ding ding ding correct.
Sissy balls refers to genitals, specifically genitals of femboys. Another word of femboys is "sissy" hence the name Sissy balls. As well never write "Sussy balls" (song) fastly on a school computer, this can lead to you getting suspended due to "innapropriate material"