The goal for this year's display was to turn my home into a landing field for flying saucers at Area 51 which the becomes invaded by aliens. In the early planning stages, I couldn't decide if I wanted the UFO to be flying or to look like it had just landed, so I built both. The full-scale, main ship was nine feet tall and thirteen feet wide. It had three aliens (six inches tall) emerging down a ramp. The second craft was 2/3 scale and was hung twenty five feet off the ground with a rope and pulley system.
The saucers were made out of used patio umbrellas for the body, kiddie umbrellas for the dome, scrap metal/wood, pvc pipe, old garbage can lids, pie plates, empty two-liter pop bottles and lots and lots of metallic spray paint.
I dressed the scene with strobes, a fog machine, black light, gobo projector and pin spots from work along with LED Christmas lights and sound activated lasers (just glorified laser pointers). Of course, there was a half hour loop of sound effects and theme music that tied it all together. We also passed out customized business cards with all of the candy, so everything was a promotional tax write off.
It takes the whole year to develop the concept and collect the supplies (mostly on eBay or from junk in the basement). Of course, the challenge is to make it cool while spending as little money as possible. I also like to keep it family friendly (no blood or gore), but still give it an edge. It took about two weeks to construct in my spare time, and then six hours to assemble on Halloween day. Over two hundred trick-or-treaters showed up along with hundreds more parents, family and friends. With the support of my neighbor who set up his own Mutex Lab display a couple houses down, the whole block had an awesome party atmosphere. Let me know if you have any questions.