Cut sports-themed ball in half with the sharp knife. Cut small slits on top of each half big enough for the headband to slide through and fit snugly.
Secure headband by wrapping a rubber band on each side of the headband within each half of the ball to ensure that the headband does not slide out.
Add the stuffing to the inside of each half of the ball.
Your warm, sporty earmuffs are ready to wear!
Optional: Headphone earmuffs
Sew a small pocket into the fabric before securing it on the half of the ball.
Place the headphone speakers into the pocket and sew around them to hold them in position.
Glue the fabric as in Step 4 with the headphone cords downward.