Her secret identity

"You also told me you aren't actually a human, but a sexual pleasure robot designed for sex."

"I am," Buffy said confidently. "But I still feel human."

"That's because you're in human mode right now. You told me the switch word to swith you between your human and robot modes. The safe word is 'Sexy Times Go.'"

As soon as Wally said that, Buffy stiffened up.

"I am Buffy-bot, how may I serve you?" she asked in monotone.

Wally smiled.