A great addition to your Riddler costume. I made this one for my boyfriends costume (he went as the Riddler and I went as Harley Quinn). For the rest of the costume use a green coat (I stray painted his) and a hat and you're good to go! I found the tie on ebay for a few dollars and got matching ribbon for the hat at a craft store. I also cut out black felt question mark and hot glued them to the coat.
To start find a picture of a question mark online to print out or free hand one. I made mine about the size of the printer paper.
Cut out the question mark and trace it onto a piece of cardboard twice. I used a cereal box. Then cut out your question marks. Next cut out a couple one inch strips of cardboard the length of the box.
Now heat up your hot glue gun and prepare to situate your pieces. You are going to glue the one inch strip to the outside edge of one of your cardboard question marks.
After you have the one inch strips glued all the way around the first question mark, set your second one on top and glue around the edges. I glued four sewing pins to the inside to stab into my Styrofoam ball.
Glue your Styrofoam ball onto your wooden dowel. I used a 1 1/2 ball and a 3/4 inch by 36 inch dowel.
Stab your pins into the Styrofoam ball and hot glue the edges to secure. (click on the pictures for a closer look)
Next take your plaster wrap and cut it into small strips. wet each strip in a bowl of water and then smooth onto the ball and question mark until it is covered. You could also use paper mache instead.
After it is dry paint with gold paint (or whatever color you would like) and you're done. You could also sand it first if you would like to get out some imperfections.
Note: Be careful with your cane, if you put too much weight on it or hit people with it you might break off the question mark and have to glue it again.