I start every costume creation by finding an example that is done often, but not to an extreme level. I saw that the only unicorn costumes online were baggy store bought suits or a horn duct taped to someone’s forehead. I knew I could do better and add an X-Factor like fog snorting out the nose.
Step 1: Foam Foundation
You can then use your expanding foam to get a bulk structure for rounded areas.
Step 2: Foam Carving
Once you have it roughed out, move to an electric carving knife which you can find at a thrift store also for about $10.
Then comes the dremel for the concave portions.
Finally I get the details done with a mesh drywall sander and dry wall spackle.
I also attached a photo showing a foam lego head I made last year to show the rough carving.
Step 3: Upholstering
Step 4: Amazon Shopping and Lighting
You can see from the video that I mounted LEDs and fiber optic lights all through the mane and in the horn to give the magical rainbow effect. If you do the fiber optic hair extensions, you'll want to cut it into multiple layered lengths or you'll just have a hard line of color at the end.
Step 5: Fog, Confetti, and Spandex
I took a typical can of compressed air. Remove the top trigger portion. Fill the hole where the air typically comes out with hot glue (don't use too much or you'll clog the whole thing). Drill a hole through the side into the path of the air. Insert your the tiny hose tube that comes with the can, hot glue and silicone into place.
You can then take a threaded rod and screw it into the tip that you filled with hot glue as a trigger extension.
I mounted the can of air in the head using a plumbing mount, screws, and gorilla glue.
IMPORTANT: The can must be mounted upside down or at an incline so the liquid gas is shot out.
CAREFUL: If liquid leaks out of the can it will burn any skin it touches. YOU'VE BEEN WARNED!!!
For the body of the costume, I originally got a morph suit and airbrushed on details. After some demo runs I bought some spandex pants to double layer. No one wants a "blow out" when you're dancing your unicorn butt off in front of 1000 people.