Well, the only way to react to someone playfully whining is to coo obnoxiously and reach over to try and pinch her cheeks. Whether she lets him or not, Joker won't force the action. It's all in good fun.

"Awww, lookit ya. What if we have ta make a stop and charm a handsome king inta lettin' us peform, and he'll only let us do it if we gets ta see the beautiful Scout in the frilliest dress?"