When everyone first met BJ, he wore clothing that hid how he looks and went by “Admin”. After hearing from Thalia that she had sex with him, Midnight determined to get him to reveal his face. Eventually he did, but Midnight was surprised due to misleading hints from Thalia. So that’s how everyone found out what BJ looks like, also the fact that he and Sky are dating. :P
Drawn by  Brahkest !