Extension cord. It doesn't actually have to be short; I just bought a short one because it was cheaper and I have plenty longer ones already that I could patch this into. I also prefer to have the fluorescent starter close to the outlet so that it's out of the way and not likely to get stepped on. You can pick up 6 ft. cords for less than $5 almost anywhere (I think mine were about half that much).
Fluorescent starter. These are normally present in fluorescent light fixtures. They are used to ignite the light, but this circuit takes advantage of the fact that they will keep cycling through an almost random series of attempts to light an incandescent bulb. These starters can be found at any hardware store for a couple bucks, usually in packs of two. I use FS-5 starters in mine, but I have read that FS-2 will work also (not tested by me, however), although FS-4 starters should be avoided as they will not produce the desired effect.
Electrical tape. I use this to seal up the starter onto the extension cord and insulate everything.
Cut one of the wires and pull it back almost a full inch (as pictured). Do not cut the other one.
Pull the ends of the cut wire free from the intact wire so that you have some slack to work with.
|Wrap the exposed wire around the lugs of the fluorescent starter.|
|Use electrical tape to go around
the sides of the starter and hold the
wires there. Then just keep wrapping until all the exposed wires
Note that this isn't an especially waterproof approach, but you can use waterproof electrical enclosures for outdoor use. Plug everything into a GFCI outlet regardless, just to be safe.
Alternatively, you can find sockets for the starters, but they're around $2.50 each (at least) compared with $1 per starter. I just went with the tape so far and no problems in three (update: make that five!) Halloweens with several of these around the house and even in the yard.
Sorry I don't have any animations of my lights in use with this effect, but there are plenty of videos of them in use on YouTube. See here and here, for example.