Because I can think of some great sidekick names. Question Mark Girl. Riddle Lass.
My concern is why he'd want to emulate a Joker that isn't him. Regardless, I'm going to dig into unusually large purchases of chemicals used in our Gotham to make laughing gas. Might need you to place some Riddler cameras in the Industrial District if you're up to it.
Working alone allows me to be more artful, but I admit it's less exciting. You've never worked alone, have you?