I decided a few years back to be Jack In The Box for Halloween. I started 3 weeks early in preparation. In the end, I wished I had one more week to clean it up around the edges. Bear with me, as the process of making the jack head was tedious.
To make the jack head shell, I bought a bouncy ball at Walmart about one foot in diameter. I then began the paper mache process, which I completed 1 layer each week, for a total of 3 layers. Ideally, a 4th layer would have provided more structure. After the paper mache had dried, I cut a circle at one end of the sphere, and this was to be the head entry point. The circle was 8? in diameter. I then removed the rubber ball (skeleton) from the paper mache shell very carefully.
On the exterior, I sprayed on 3 coats of white enamel spray paint. This left the jack head looking much like a moon given the topography of the dried paper mache. I then purchased a thick, white, stretchable fabric from a fabrics store (similar to jersey material, but I cannot remember the name). I cut a hole 3″ in diameter at the point where the hat was going to go (somewhat offset from center). This allowed me to stretch the fabric from the head entrance to the hat hole. I carefully used a stapler to secure the fabric to the shell, which gave it a very smooth appearance.
For the eyes, I cut 2 holes in the shell about 1.5″ in diameter. I then cut 3″ diameter circles from transparency paper and covered the circles with cheap blue fabric using super-glue. I couldn’t see much, but I could walk around without bumping into a wall.
For the nose, I used black construction paper to create a cone by wrapping. I taped a base inside the nose and secured the base to the fabric with superglue.
For the mouth, I bought a red sheet of felt with adhesive backing, and cut a smile out of it. This stuck to the fabric easily without additional glue.
For the hat, I found a small, child-sized megaphone. One coat of primer spray paint, and one coat of yellow spray paint did the job. For the brim, I used construction paper, which was also spray painted with the same yellow as the cone. You’ll have to figure out the correct measurements so that when you cut the ring, it has a good angle (somewhat less than 45 degrees). Both were super-glued to the shell.
Last but not least, I bought a sturdy straw hat (in a child size), and super-glued the top of the hat to the inside top of the shell. This allowed me to wear the hat, and not the shell. You’ll have to experiment with spacers between the shell and the hat so as to prevent the shell from resting on your shoulders.
It took many hours over 3 weekends; buying multiple supplies, and waiting for paint and mache to dry. I highly recommend the idea, as it was a real hit to the parties I went to. I took pictures with lots of people, and nearly everyone wanted to try on the jackhead. The Jack in the Box homemade costume is a sure bet for a Halloween contest if you can pull it off.
Related costumes:
Winning Google Android Costume 
Coolest Kia Soul Hamsters Couple Halloween Costumes 
Easy No-Sew DIY Kool-Aid Man Costume – OH YEAH! 
Coolest 7-Up Cool Spot Costume 
Cool Jack in the Box Halloween Costume 
Coolest Jack-in-the-Box Family Costume 
Coolest Jack In The Box Halloween Costume 
Cool Jack in the Box Costume
Are you willing to sell the head?
I made that jack head about 5 years ago. It held up for a few years but ultimately fell apart. I’d have to make a new one, and at that, I recommend you enjoy the experience of making it yourself!
I’m making the Jack head and I was wondering what you used for the inside of the head? When you put the head on did you fill it with something or did you just wear it as is?
I found a small child’s straw hat at Walmart and glued the top of the hat to the inside-top of the Jack head. The straw hat was comfortable enough to wear for long periods, but sturdy enough to hold up the Jack head. You could probably go with any hat that has a similarly strong structure.
The straw hat inside allowed me to wear the hat, which sat atop the crown of my head, instead of just placing the Jack head over my head. Without the straw hat, the Jack head would sit on my shoulders thus removing the appearance of my neck. For authenticity, it’s crucial that the head appears centrally placed with the neck showing. I didn’t fill the hat with any material or make any aesthetic modifications — it was just a hollow ball of paper mache.