Step 1: Materials (necessary and not-so-necessary)
We got through a fair bit of this. They come in large 8 foot by 2 foot sheets. They're meant for housing insulation but they also work great as the basis for lego heads. They also provide maximum fun while carrying them back for 20 blocks through a windy New York October. Depending on the proportions of your body size, you'll need to adjust your head size (and amount of polystyrene) accordingly.
Fans, Battery and Switch
All from radio shack - as I was building these heads I realized how ridiculously hot they were going to be inside. The fan was meant for a computer and the battery was a 9 volt with a small switch in between. If you're going for the less complicated route, this would be the thing to skip. In fact my better half was shocked that I was putting time and effort into such an elegant solution. Hey, it was worth it on the night!
Again, we tried to match an actual lego head as closely as possible. Home depot was our supplier in this case. Vast quantities of yellow and black (Groom) and yellow, white and black (Bride).
Step 2: Cutting Heads
The most important part of making the heads was the preparation. We took a picture of a mini-fig off google, printed it out, and made it into a kind of grid, with the proportions based on a 6 foot tall boy and 5 foot 5 girl. We made the decision that even though we're different heights we'd make the heads themselves the same dimensions. When you scale the mini-fig dimensions (e.g. width of head and height of head including 'bit' on top of the head) to human proportions, they really are bigger than you think. Don't back down at this point and think 'oh well make them smaller', they really do need to be that big to get the slightly 'square' look of the mini-fig.
Once we had the dimensions (the head was about 15 inches 'wide' - diameter in the end) we went ahead with planning the cutting of the circles into the sheets of polystyrene. Our heads landed up being made of discs which were 1 inch thick - 2 discs around the neck, 13 discs high for the main part of the head, and 3 discs high for the 'bit' on the top of the head. Total of 18 inches high, roughly... I actually just measured it and it looks like they've either squashed slightly or they were always slightly less than 1 inch - total height is about 17 inches.
Work out how many discs you need, and what sizes, then it's just a matter of drawing them out on the huge sheets of polystyrene without wasting too much in the gaps. We had to keep going back to the hardware store because we underestimated. Then the hardware store ran out, then we had to go to hardware stores further and further away... fun!
A craft knife / box cutter with the blade pushed out so that it easily reaches through the thickness of the polystyrene works easily for cutting out the discs. We drew the circles using a pin and string with a tiny loop tied into it at the appropriate length. High tech stuff.
I cut out the discs 'whole', so no hole in the middle at this point. At the end of it, i had a stack of correctly sized discs that i could pile into a shape of a lego head. Due to either my drawing skills or my cutting skills I landed up with very slight differences in the discs, so at this point I spent a while shuffling them all into the optimum order and orientation so that they were pretty much all perfectly lined up. At that point, I drew lines on them and numbered them so that I could put them back together in the right order and orientation. Probably in my sleep.
Step 3: Fitting and Gluing
The next 12 discs were basically trying them on my head, cutting, trying it on, cutting more, trying it on, gluing, then next disc. Gradually working my way up to the top of the head. HOWEVER I did make some just-in-time adjustments for the fan, switch and battery at this point, which is waaaaay easier to do when you're still cutting the individual discs, not when they're all glued together. See the next section!
Step 4: Battery and Switch for the Fan!
I've drawn an equally dismal sketch of a top view of discs 7 and 8. You can see the battery size hole where the battery actually finally sits in disc 7, and the disc above (disc 8) you can see where the hole is where you slide in the battery from the inside. The mess underneath is the side view of someone wearing the head, with the tetris shaped hole in the right where you slide in the battery and it goes down to the lower disc level.
The end result of these placements is that the battery is nice and safe, and away from rain etc, and the switch is nice and accessible right by the neck, where you can easily fit a finger up between your neck and the neck discs to flick it on/off as needed.
Step 5: Fan Placement and the 'Bit' on top
I didn't want to skimp on details, so even though both of us would be wearing something on top of the heads, I wanted the 'bit' on the top of the head to be proportioned correctly. These were the 3 smaller discs on top of the head. Again there was a hole cut in these, not because anything was going there, but so that fresh air could be sucked in from the outside and pushed through into the head itself. I also added black mesh to the middle disc to keep out anything from fluttering through in case it somehow got through to the head and the fan.
Step 6: Finishing Steps
One thing I would do differently - the polystyrene sheets have plastic backing on each side, which kind of comes off, but doesn't really. We tried to peel it off, but when it was so difficult we left it, figuring it wouldn't harm as we'd be hot-gluing them together anyway. The only point where this became a problem was when we were sanding down the sides of the head. We found that the double edge of the plastic between the discs was just enough to stop it fully sanding. So we had to painstakingly use a knife around all the disc joins to attempt to cut out the plastic edges. I think this is why you can see the joins between the discs more than you really should.
Step 7: Painting and Head Accessories
Painting the heads and eyes (I went with mesh in my eye pieces, Jeni declined for added visibility) was pretty self-explanatory. The top hat and the bride's veil were made in the same way as the heads, with discs of polystyrene. Both 'snapped' perfectly onto the dimple on the top of the lego head by making sure the outside ring of the top hat fitted snugly to the outside of the head, and the inside piece of the hat had an opening for the head-top dimple to fit through.
The other consideration was that both the hat and the veil had vents in the top (more subtle on the veil, and just a circular hole with mesh on the hat) to allow fresh air to be pulled through into the head space by the fan.
Step 8: The Body Part of the Costumes
The front of the groom had the white areas cut out of poster board (it looked like a wiggly martini glass) and stuck onto the black vinyl body. This was drawn freehand on white poster board, then cut out and glued to the black vinyl.The flowers were then made from leftovers - a nice touch for a late night wedding parade down in the village. Leftover polystyrene made the flower heads themselves, and rolled up card for the stems.
The hands were cut from Quaker Oats canisters. Two layers for each hand, with a large hole to slip your hand into on the back layer. Once assembled, they were also painted yellow. Simple yellow kitchen gloves were used to cover our hands and wrists.
Step 9: The Final Result
Fans? Definitely worth it - they get really hot in there. I guess the stuff that they make to keep houses warm/cool also insulates human heads very well. Everything held together well, and I think the only running repair was chewing gum applied to one of the flower heads that slipped down the stem at one point.
We even made it into a movie - 'Fat Sick and Nearly Dead'... a random shot of the NY halloween parade included a side view of us!
Would definitely do it again!!! Hope you enjoyed reading, and hope you have fun if you decide to give this a try.