The UFO

Disclaimer:  I have nowhere to store props from year to year, so they get tossed after Halloween.
Because of this, all props you see are made to be cheap but NOT very durable!

Click on pictures for a larger version.
 
 
For the main section of the flying saucer, we bought a cheap child's wading pool and cut a large hole on top for the "bubble" and smaller portholes around the side.  Because of the way the ship would have to be mounted on the front of the building, we only needed to use one pool.  It was then painted with cheap, silver spraypaint which was highly prone to cracking and chipping, but since no one would see it up close, it wasn't a problem.  The inside of the ship was covered with two coats of spare latex paint to keep the image of cartoonish sea creatures from showing through once the interior light was in place.  
  Here, Thunder is lightly spraypainting squares of tracing paper.  These were taped with strong, clear packing tape to the portholes from the inside.  A light fixture would be placed inside the ship, making the portholes glow bright green.
A clear plastic dome whose original purpose remains unclear was used for the "beacon" on top of the ship.  Red gels were stuffed inside, followed by clear, flashing Christmas lights.  The whole thing was then taped from the inside with MASSIVE amounts of duct tape.  Next, two fullsheets of 1/2" plywood were each cut into semi-circles then painted silver (after a sealing coat of grey latex paint).  The two halfs were joined together with a large scrap piece of plywood in the center, with smaller, inconspicuous pieces attached at the ends.  Two holes were drilled through the center for mounting purposes.  A light fixture and bulb were attached to the center wood support.  Finally, the upper section of the ship was attached to the wood using a heavy-duty staple gun; the electrical cords for the lights were run out from one of the holes underneath.  
  Next, a string of blue Christmas lights was attached to the edge of the saucer section with clear pushpins  We had hoped to use chaser lights, but they were impossible to find on short notice.  We set the string of lights to flash instead. Last, a length of strong rope strong rope was strung through the holes at the center of the saucer section.  These ropes were used to hoist the ship up onto the balcony of the building, and to secure the ship to the building by tying them to nearby metal rails.  All of this was hidden from the view of partygoers in the courtyard by a large sheet of black plastic covering the opening.  A fog machine hidden under the ship provided the "smoke" from the crashed ufo.

The Alien Autopsy