Sew two pairs of pants. One of cotton in the correct size and one of fur in a larger size. Make the pants shorter than normal (ending about an inch below the middle of the calf) and elasticize the bottoms and waistbands.
Put the cotton pants on your client (or a model if they are for yourself). Use a pen to draw large ovals which cover the upper thighs. Then draw rectangles which cover the calf from directly below the knee to about halfway down the calf.
Sew two oval pillows (the size of the thigh circles) and stuff them with the batting. Make your pillows flat on the bottom and round at the top (making the bottom oval a little smaller than the top one may help). Sew two pyramid pillows. The bottoms should match the rectangles you drew.
Carefully hand stitch the pillows into position on the cotton pants. Pull the fur pants over the cotton ones and carefully tack together if desired.
Cut out two tail shapes from your fur scraps. Sew them together and stuff slightly. Carefully sew onto outside of fur pants in correct position.
On your felt, draw two hearts four inches tall and wide. Add a 'stem' to the top of the hearts, make it and inch and a half wide and two or three inches long. Wrap the stem of the heart around the side of the headband and stitch it on (bending the heart to create a cup while you do so) to create ears.
Unroll your paper towel rolls and give them a quick coat of paint. Attach these to the top of the headband to make horns.
Put on all your costume pieces and prance out to praise and applause.