Harley most definitely writes fanfiction about herself and Joker. She’s not getting much in real life, so she makes it up. She rewrites the whole story of her breaking Joker out for the first time and turns it into obnoxiously cheesy erotica.
“It’s only natural you’d be attracted to a man who can make you laugh.” Joker said as his hand made it’s way up the doctor’s thigh. “What else can you make me do?” Harleen replied in a deep breathy voice.
And Joker finds this smut one day and is like “HARLEY WHAT IN GODS NAME” but inside he’s a little like ( ͡° ͜ʖ ͡°)