Nothing special. I just chose a moment from "Batman Beyond:The return of the Joker" and drew it! (clearly, those characters belong to DC comics).
P.S. Harley and Mr. J are sooo sweet together, aren't they?
P.P.S. For those ho may be interested: I drew all the lines with a pen, then scanned it and coloured in Photoshop, using my laptop and a touchpad which is built in it's body