Here's an effect that I bet a lot of people have not seen, its the "Witch Doctor Illusion". It is available from Abbotts, but they do not make these up ahead of time, only special orders.
Usually this is done with a live spectator, however I demo'd it with a skeleton to spookify it a bit. The advantage of a live spectator is that they can move and talk and the effect really looks weird when that happens. If the person doing the effect is known before hand, have them talk in a high pitch voice when the head appears to be shrunken (ala the conclusion of Beetlejuice)
The effect is pretty good on the angles, the problem this one has is lighting so a rheostat is included that allows to to adjust the lighting on the inside of the box (yes, there is a lightbulb on the inside). The prop packs down surprisingly small and comes with a case, the afore mentioned rheostat, and also a sound effect generator if you need it.
The spectator really doesn't do anything here, the box does all the magic. However the box is kind of long and not the easiest to hold so I put mine on a tripod, that way the spectator does not hold anything, and if I can't get a spectator I can use a plastic skeleton since the skeleton does not have to hold anything either.
One really big plus with this is that other head effects will work with this base. Both the Dagger Chest and the Flaming Head Chest will slide right onto this base, so putting this on a tripod makes other props versatile as well (you can see this base being used in the dagger chest demo, however I had my wife hold the flaming head chest)
The illusion may not be the strongest, you have to get the audience to pay attention to notice the shrinking, however at Halloween time this can be a accomplished easily if you dim the house lights and spot lights (The light illuminating the inside of the box really creates some spooky atmosphere under those conditions). The prop does requires 110 volts so you will need to have wires or extension cord going across your stage area so be prepared for that. If you try doing this in a niteclub or bar atmosphere, the effect is not as strong.
Below is the sales ad for Witch Doctor (Abbotts Amazing Shrunken Head Illusion)
A thin wooden tray or platform is displayed. Mounted at one end of this tray is an open framework. At the audience side of this framework is an opening nine inches square.
A spectator is invited onstage and is seated. This spectator holds this wooden tray on his shoulders (there is a cut out provided for his neck). His head is completely visible, at this point, from all sides - including through the opening of the framework. The performer then covers the spectators head by extending a folding expansion bellows (made from reinforced fiber stock) from the framework back and over the spectators head. An electric light is now turned on (accompanied by a futuristic sound effect), illuminating the spectators head inside the cabinet.
A thin, decorative panel is inserted behind the opening of the framework. another strange sound effect is produced. The spectators head is out of sight for less than one second! The panel is immediately removed. Inside the cabinet - the same spectator - the same lighting - but the spectators head has shrunk to half its original size! A sensational and startling transformation! Points to remember; The spectator can smile or frown - wiggle eyebrows - make his nose twitch - wiggle his ears - stick out his tongue, etc. The interior light is connected to a dimmer switch to produce special lighting effects, if desired (more light, less light, etc.)
The unit is slowly turned from side to side so that all in the audience can witness this strange effect. Completely safe and completely baffling!