My daughter wants to be a horse rider for Halloween, so I turned her bicycle into a “horse”. It was easy to do and not very expensive. All I needed:
10 foot (3m) LED light string. The one I got is USB powered, I paid $10.
12.5 gauge solid steel wire. I found a spool at a hardware store for $10, the spool had 10 times as much as I needed.
Clamps and bolts to attach the wire to the bicycle.
USB backup battery to power the lights.

Step 1: Install Wire

Cut two pieces of wire about 6 feet long. One piece will make the body and tail, the other piece will make the head and is attached to the handlebars and front fork. On my daughter’s bike there were holes in the frame near the front and rear brakes that I could use for mounting. For those I bent the wire into a loop and used a nut and bolt to attach the wire to the frame. On the other end I used hose clamps to hold the wire to the frame. I put tape around the bike frame where I was going to clamp to avoid scratching the paint. Fasten one end of the wire to the frame and start bending the wire into the horse shape. When you get to the end, cut off any excess wire and attach the other end of the wire to the bike. You can tie the wire to the seat post with a twist tie to help hold it.

Step 2: Add Light String

Attach the light string to the wire using twist ties. Put the plug end of the light string at the back of the bike. When you get to the point between the body and head, go from the stationary body part to the turning head part exactly over the axis of the steering. Use tape to attach the battery pack to the frame and plug it in!