Make your paper mache paste, using a one to one ratio of water and flour. The paste should be a thick glue like texture. If it's too thick, add a bit more water. Tear the newspaper into long thin strips. Fully inflate a 36" balloon with air and set it on something like a box to keep it from rolling around.
Begin your first layer of paper mache. Dip each strip of newspaper into the paper mache and squeeze off the excess with your fingers, then place on the balloon. Cover the entire balloon in one layer and let dry completely.
Repeat three more times so you have four layers total. This is really important so the ball is nice and sturdy for the costume. Once the fourth layer is completely dry, deflate the balloon and you'll be left with the base of your magic 8 ball costume!
You'll need to cut a hole in the top and bottom of the magic 8 ball that is big enough for you to fit through. The bottom hole should be a bit wider since you'll need to be able to move your legs so you can walk.
Paint the entire ball black and let dry.
Paint a white circle on one side of the ball. Let dry, and then paint a black 8 over top of it.
On the other side, paint a gray outline of a circle and let dry. Then paint a blue triangle inside the circle. Let dry again. Finally, paint any magic 8 ball phrase you want on the back!