Wash and dry the t-shirt as needed. Insert paper inside the t-shirt to protect the back side.
Use Mod Podge to paint a lightning bolt shape on the front of the shirt. Fill in the shape with Mod Podge.
Sprinkle glitter over the top. Shake off the excess and let dry. If you shake the glitter onto a piece of paper, you can put it right back into the bottle.
Cut the felt to fit the child's wrists. Repeat step 2 on the cuffs, making smaller lightning bolt shapes.
For the wrist cuffs, either use Velcro to secure if you want them to be reusable, or attach them with glue the day of. You can cut or slip them off later.
Spread a coat of Mod Podge on the mask; sprinkle glitter. Let dry and shake off the excess. Let dry.
To make the skirt, cut a piece of elastic to fit the child's waist. Hot glue into a loop.
Line up the tulle pieces one on top of the other. Trim the edge so that when doubled over, it's the desired length (for example, if you want a 15" skirt, your strips need to be 30" long). I cut strips of all five colors at one time.
Attach tulle strips to the elastic strap, one by one. Make a loop halfway down the tulle strip, wrap around the elastic, and pull the two ends through. Work your way around the elastic.
Push the strips tightly together so that when the elastic is put around the waist, the skirt is full. Add a boa or anything extra you desire to complete the costume!
Notes
I already had a lot of the supplies on hand and only had to purchase the tulle; costs will vary.