Zoe was in the way, so Jon couldn't see the guy's face, but it was clear from where he was standing that the person outside the house was Steve "The Stud" Farber, a womanizing jerk who went to school with Jon. But when Zoe moved out of the way, Jon saw that Steve didn't have his face. Instead he had the face of Athena DeVries, Zoe's best friend. And judging by the bulge beneath Athena's pants, Jon figured that Athena was male.
He didn't get it. At first, he thought that everything but the person's face, mind, and sexual organs switched with someone else's (judging by what happened to his mother). But if that were true, then Athena would have female parts. As it was, she didn't. So didn't that make Athena a "he"?
"Hey, Athena," Zoe said, smiling.
"Hey, babe," Athena replied. Jon was confused again. Athena had her own voice, not Steve's. And the way she talked, it almost sounded like it was Steve who was talking, not Zoe's friend.
So, Athena had her own voice and face, but had Steve's body and mind? Maybe whatever was happening was more complicated than Jon originally thought.