Here is a robotic skull with motion detection that lets you play tricks on your visitors. The robot is 3D printed and has a motion sensor to animate and scare people close by. You are going to need a MakerClub Hornet Microcontroller, Tower Pro Micro Servos, PIR motion sensor, LEDs, batteries, and a few other components to get started.
WilliamB123 has shared more info about this project here.