Lets create some egg carton mushrooms. What you need: egg carton, cottons, white manila card, glue, scissors, paint brush, and washable kid's fingerpaint.
Cut egg carton into individual cups. Paint the egg carton cup red then paste the cottons on it while it's still wet. The cottons somehow will stick on it. Cut the white manila card into small rectangle then roll and glue it (look like a small toilet paper roll). Last step is to glue the two parts together as picture below.