Adam and Eve. Beauty and the Beast. Bonnie and Clyde. Boring. If you're in search of an interesting and unusual couples' (or siblings') tandem costume for Halloween or a costume party, consider dressing up as the classic Nickelodeon cartoon character CatDog. Aired on Nickelodeon from 1998 to 2004, CatDog was sort of a Laurel and Hardy routine in the body of a cultured and cunning cat and a happy-go-lucky dog, joined together at the torso.
Paint large orange spots onto the blanket, the sweatshirts and the leggings. Allow to dry.
Roll the blanket into a tube, with the spots facing out and the tube's openings approximately the size of the sweatshirts' backs. Sew the tube shut with a straight stitch 1/4 inch from the exposed edge of the blanket.
Stuff the blanket tube full of batting so it maintains its shape.
Sew one end of the fabric tube to the back of one of the sweatshirts using a double stitch so the tube covers as much of the shirt's back as possible. Then repeat with the other side of the tube on the other sweatshirt.
Cut a nose-sized hole out of each ping pong ball, and poke two additional smaller holes on either side of each one. Cut two lengths of elastic string large enough to secure these to a person's head, thread each one through the two small holes in one of the balls and paint one of the balls blue and the other brown. Allow to dry.
Cut two long pear shapes -- floppy dog ears -- out of the yellow felt, and paint a few orange spots onto them.
Cut four triangles out of the yellow felt and two triangles the same size and shape out of the cardboard. Glue a felt triangle to each side of each of the cardboard triangles. Allow to dry.
Sew the cat ears onto one sweatshirt's hood, and the dog ears onto the other.
Paint the sneakers yellow.
Have each person put on the sweatshirts, leggings and sneakers. Put the blue nose on Dog and the brown nose on Cat. Draw whiskers on Cat's face with eyeliner.
For maximum accuracy and minimum practicality, cut off the arms of the sweatshirts and sew the holes closed. CatDog does, after all, only have four limbs.
Since the costume is meant to be worn by two people simultaneously with their backs to each other, spend some time practicing how to walk and move so it doesn't get ripped apart.
Fabric paint is ideal. Read the instructions carefully, however, as some fabric paints need to be ironed on in order to become permanent.