Description: I wanted a nice progression of nasty alien things from dead-in-jars to alive-but-small-and-captive to alive-and-big-and-escaped.
The "life cycle" of this nasty thing is microscopic spore to slime growing from flesh to alien colony. In the last room of the haunted house will be the escaped alien growth having killed a scientist and starting a large colony from his body. This creature wasn't too hard or expensive to build.
I won't go into details on how I made this small colony. I used Skulpey to make the egg pods and the small stalk creature. The teeth for the creature were tips I cut from some fishing lures. The slimy growth is Great Stuff spray foam. I then painted everything with glow-in-the-dark paints. I did not try to cover the spray foam entirely with paint. The foam has a natural yellow color which complements the green paint. Anyway, to add a little interest, I drilled a hole through the bottom of the egg pods and poked a fading-orange christmas light bulb through the bottom. This way, a pulsing orange light eminated from the interior of the egg. I tried to get a picture for the black light lit colony but the picture is out of focus. Sorry.
To make the head of the giant creature, I bought a 8"-to-4" air duct adaptor from Home Depot for about $5. I placed the large end down on some wax paper and arranged eight worm fishing lures in a circle on the inside so that they were pointing towards the center. I then sprayed a thin circle of Great Stuff foam along the inside rim to "glue" the lures in place. After 2 hours, I turned the adaptor over and spayed more foam over the top edge of the adaptor. When I was finished, it looked like this.
I was surprised to find that you can buy 10 feet of 4" corrugated plastic pipe for less than $5. I used that for the body and some 1" plastic tubing and coat-hanger wire for the antenna. To hold the creature in place, I used wood screws for the body and fishing line to hold up the head. I then used masking tape to build up the area where the antenna meet the head of the creature. Before I screwed the body in place, I used a hacksaw to cut a hole large enough to fit my hand in in the back of the creature where it meets the back wall. This will allow me to pass candy through the creature.
I added more spray foam inside the mouth and painted it red. I probably should have done this before I attached it to the body so that I could do both the top and bottom of the mouth. Live and learn. A bit a red paint and the mouth looks pretty nasty.
For the body, I used paper towels and a mixture of 2 cups water, 1/4 cup flower and one bottle of Elmer's Glue. I wet the paper towels with the mixture and wrapped the plastic piping. After it dried, I spay-painted it fluorescent green. One note about spray-painting in a garage - it is a mess. The paint will mist and settle on everything. So, i you are going to do this, make sure you use plenty and drop cloths and contain the area the best you can. You will notice that their is plenty of white left. This is because I was trying not to make a mess rather than making it two-toned. In the black light, no one will notice.
You will notice the dead scientist. I was lucky enough to get an old "bunny suit" from work. These are the suits people wear in a clean room when manufacturing computer chips. I make a simple jointed frame with wood to hold his legs in a natural position then stuffed it with paper. I got the fake hand from a Halloween shop. The head I filled with spray foam and put foam all over. A little paint and he's done. Note that I used three different colors of paint (the foam itself makes four). This little detail adds a lot for realism.
I like to have the monsters pass out the candy. I got some stiff plastic tubing from work and attached an alligator clip to the end of it. I then painted the "tongue" green (I made four of these, actually, so that I can pre-load them and pass out the candy more quickly). If you look closely, you can see part of the hole in the plastic sheet where the creature's back meets the wall. This is where the hole in the creature's back is.
And we are done. Some black lights and a red rotating siren light puts everything in the right mood.