We have a plywood witch built a few years ago and decided to add a black cat with glowing eyes.
(Looping is imperfect on Vimeo, sorry!)
Step 1: The Body
The cat was cut out of 1" foam, covered with a cotton sheet and painted with waterproof paint then acrylics (see our Steampunk Gears instructable for technique). Plywood gussets are glued with urethane glue to the back for stake ties and to mount the electronics.
Eyes are cut from scrap acrylic sheets with parchment paper behind. The pupils are thin brass because the LEDs are so bright - even thick paper does not block the light.
Step 2: Electronics
Making the eyes flash occasionally adds a fun surprise. I used a 556C (Dual 555 CMOS) timer to give 6 quick flashes then wait 5 seconds. I breadboarded it quickly then did a one-off circuit on a breadboard layout PCB material. A 12V 600mA wall transformer supplies power - batteries wouldn't last night after night.
The LEDs are in a light-proof box, the circuits are in a plastic snap lid container.
Step 3: Ready for Halloween
It goes perfectly with our witch. Click on the last image to see what it looks like with the flashing eyes.
Make your own menagerie!