Step 1: Assemble Tools and Materials.
1/2" foam - could be as little as a yard and a half; more means more spikes & longer tail
Purple stretch velveteen, about 6 yds, I think. 60" wide. I had substantial remnants.
6" x 6" piece of black netting
Felt: white, red, and black
Black permanent marker
Step 2: Make Wire Tube and Crimp Into Sphere.
Using my hands, crimped the top edge every few inches to round out the shape. Made kind of pleats in the wire that I flattened against each other. Then threaded very flexible aluminum wire through this edge to hold it.
Did a similar crimp around the bottom edge but didn't run wire through so it would expand over head and shoulders for installation/removal.
Step 3: Make 'ear' Spikes and Attach.
To attach I cut several 3-inch pieces of aluminum wire, poked them through the edges of the cones and twisted them around the chicken wire frame. This also provided a surprisingly sturdy result. Two wires worked for every cone I did; I added more for greater durability (a few of the aluminum wires eventually broke after several vigorous dance-filled party wearings).
Step 4: Make Shoulder Straps.
We tested the strap location at several places using clothespins before finding the ideal spot, one of the exercises that checks your intuitive sense of where a body fits in a space. Helps to not have the top of the sphere resting on the human's head. And having the sphere slightly higher made it easier to walk (and dance!).
Once aligned, straps were wrapped around several wires and fastened with more duct tape.
Step 5: Sew, Attach Fabric Cover.
Once sewn, I slipped it over the sphere with extra at both top and bottom.
At the top, I began to drape the extra fabric over the ears, and might even have 'tied' a few spots down with aluminum wire ties, but didn't worry too much about it at this point. The fabric was eventually readjusted anyway when I added the addition spikes near the end.
Step 6: Make Arms.
The end piece was 2-dimensional though the arm itself was a cylinder.
After sewing the arm, I cut the seam allowances and used it to cut the foam for the fingers.
Guessed a bit on the size of the arm cylinder, trying and adjusting before using spray glue to seal the edges together. Made the cylinder insert shorter than the fabric so there'd be extra to both attach to the body and tuck over the ends. Wanted to have the cylinder's circumference just big enough to stretch the fabric and keep it smooth.
Used short bits of wire to attach the arms. Again, even just two points seemed sufficiently stable, but added two more to account for vigorous handshakes and potential doorway encounters.
Step 7: Make, Attach Tail.
Step 8: Cut, Glue and Attach Face.
Ultimately the mouth looked even better with a thicker outline around it. I'm sure there's some marker that's even better for felt, but we didn't have one in the house. Went over the lines several times.
Step 9: Make and Attach Various Other Head Spikes.
Attached them as they best fit between the 'ears' and tucked them down the back, draping fabric over and pinning it down with the wire.
This was the loosest piece of the setup, in that I left some opening so we could see down into the human space and let some light in (before the netting peep hole innovation at the end). Imagine you could be much more thorough than I was.
Step 10: Make the Peep Hole.
With costume off I cut a U-shaped flap in the fabric and placed a square of screen door fabric (cloth, not wire) under it, attaching again with wire bits. Eventually we folded the flap out of the way for constant visibility. I was surprised by how little it detracted from the overall effect, although in bright indoor lighting it was pretty apparent. Outside it seemed to disappear.