This year, having failed to make plans requiring the creation of costumes, my husband and I decided to divert our holiday-themed creative energy instead on what is obviously be the next best thing: an animatronic Halloween Lego robot.
After assessing the available bricks, I settled on a skull that would move it's mouth up and down. The mouth was where I started, using the door frame from a Belleville door, two Belleville arch bricks designed to be bed frames, and a couple of hinge-y pieces, I soon had a great scary skull mouth with chattery teeth (take THAT, ye girl-set naysayers!)
The rest of the head I built sculpture-style until I got to the eyes, which Spongebob graciously lent me. I realized at that point that of course in addition to the mouth, we could also make the eyes move, using the same Technic setup from Spongebob's instructions. I added all the necessary pieces and gears, and then created additional gearing to connect the mouth movement to the eyes, to simplify the robot part.
Meanwhile, my husband tinkered around with his Mindstorms set to program it for the needed movement. He decided on a sound-activated sensor. He then engaged his Mindstorms wizardry to get all the parts working together. He even discovered there was a default spooky laugh on there to provide our skull's voice.
When we were all finished, we had a skull that activated on sound by laughing maniacally while chomping its teeth and rolling its eyes. It was really awesome!
Apologies for the sideways-ness of the video. I have no idea how to make it stand up the right way, or if it's even possible: