Easy – you use infrared controlled Mickey Mouse ears.
The ears communicate with IR controllers and can react to certain parts of Disneyland. According to the video(s) below they have only scratched the surface and the ears will be able to interact with each other as well (they kind of do already as you can sync their lights with each other if you get them close enough).
The main attraction is the World of Colour experience where the ears are grouped into zones so the technicians can use all the “participants” to incorporate the ears into the show, think sweeping changes of colour running through the crowd.
Check out the 2 videos below
Now I just have to find the time and money to go to Disneyland myself