[Update 4/28/2011] - I've made this entry public again due to popular demand. I'm glad you guys enjoy it! There are some much, much better Katamari costumes out there, though, but I guess mine is a good place to start if you're not a professional costumer (I'm certainly not one). Feel free to get creative! I was just making this one up as I went along and had no clue what I was doing. No doubt there are certainly ways it could be done better. Anyway, enjoy! ^_^
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After desperately searching the interweb for instructions on how to create Katamari costume heads and finding nothing worthwhile, I decided to give it a shot and make my own.
The entire process took about four to six hours. I wasn't really counting. I was also making two at the same time.
Supplies needed:
Two plastic bowls with a diameter somewhat larger than your head
Lots of poster board
Felt or cheap fabric (all the colors of your character)
Plastic ball
Sharp scissors
Duct tape
Spray adhesive
Hot glue gun and glue sticks (super glue is pictured, but didn't work as well)
(Optional: Paper to make face; Self-adhesive Velcro to make the face removable)
Step 1: Overlap the poster board and tape it together to add thickness and length.
Step 2: Roll it into a cylinder with the same diameter as the plastic bowl.
Step 3: Cut tabs in the tube a little less than an inch deep and a few inches long.
Step 4: Attach bowl by alternating tabs inside and outside of bowl's edge and securing with duct tape.
Step 5: Reinforce with lots of duct tape. Repeat steps 3 and 4 with other end.
Step 6: Cut a hole in the cardboard big enough to fit over your head.
Step 7: Try it on to see where you want to make a hole for the face, then cut it out.
Step 8: Cut fabric to completely cover tube and extend slightly over edges of bowls. Use spray adhesive to attach fabric to head.
CAUTION: Use spray adhesive outside. The fumes are intense.
[No picture, sorry!]
Step 9: Cut fabric extending over bowls into strips a few inches wide.
Step 10: Glue each strip down. You will overlap each strip over the next to keep fabric smooth.
Step 11: Cut out a circle of felt the size of the bottom of the bowl to glue over the ends.
Step 12: Cut triangle tabs for the face hole and fold them inside, attaching with hot glue and/or duct tape. Repeat for head hole.
Step 13: Attach fabric details with hot glue according to what character you choose.
Step 14: Make a cone out of poster board for antenna. Cover with yellow felt. Attach with hot glue.
[No picture, sorry!]
Step 15: Hot glue red ball to top of cone. If you don't have a red ball, you can cover a ball with red felt (which is what I had to do).
[No picture again]
Optional: Create face with paper and attach to inside. You will probably want to cut out the eyes. I used self-adhesive Velcro to make the face removable.