Not very subtly.

Inside you can see The Joker, standing on a stage in front of his brainwashed army.

"Hey Mistah J!" Harley shouts as she takes the stage next to him.

"Hello, Harley." He replies spanking her ass as he looks out to his mind-controlled masses.

"Say, Mistah J, how ye controllin' these people anyhow?" She asks, pointe blank.

"Never you mind Harley, you wouldn't understand anyway." He says, annoyed at the question.

"Oh please Mistah J!" She says, rubbing herself up against his chest, "I'm really interested. From a psychiatric point of view." Her hand slides down his chest towards his crotch.

"Oh fine, I'll explain it. But on one condition."

"Anything for you, Mistah J" She replies with a seductive smile.