With the Riddler costume hat, I got lucky and found it at a yard sale. I made the question mark out of white craft foam and painted it black and glued it to the hat. The mask was also made out of white craft foam. I painted it green and ran a piece of elastic thru it. The elastic broke, so I glued the mask to and old pair of childrens sunglasses. I drew out the question marks on a green t-shirt and painted them black.  For the staff, I took a piece of an old lamp and spray painted it black. I attached a piece of styrofoam and then attached my question mark that was cut out of cardstock.