This $1 Popcorn Costume is as easy as they come. All you need is a rectangle of white fabric (cloth diaper, old T-shirt, pillowcase, towel) and a roll of red duct tape. White duct tape will make it look more professional, but it's optional. And you'll need scissors and safety pins.
1. Fold the fabric in half and hold it up to your child, you need it to reach your child's knees. It should be wider than your child's clothing, to allow room to pin the sides closed. If your white towel is too long or wide and you don't want to cut it, just fold the excess under and secure it with safety pins.
2. Once the rectangle is the correct size, lay it down unfolded and stripe it with duct tape. I made thick and thin stripes by cutting the duct tape, but it's perfectly fine if you just make even red and white stripes. (If you choose to do a pattern, try to keep it centered.) At the top and bottom, add a red strip going across.
3. Fold it right back in half, stripe-side in. 'Sew' the side seams with three safety pins on each side, leaving a nice big space for your child's arms. The lowest safety pin should be about two inches higher than the bottom, to leave room for your child to walk.
4. Cut a neck opening along the fold, just a slit 5 inches across. Cut downwards about 3 inches down the front and 2 down the back.
5. Create a label for the front that says "Popcorn!" and a label for the back that says "Warm, Fluffy, Delicious". Print the labels if you have access to a computer and color printer, or you can make a label out of duct tape and paint the letters with white-out.