It’s a different system for the mouths and eyes. It’s a bit more involved than wiggling the nose by the performer opening their own mouths to stretch the chin strap.

I don’t know all of the technical details, but you can see it in action in the video above of the Dream Along With Mickey show at WDW’s Magic Kingdom…in particular, the section starting at 3:05 after the song and dance number.

You’ll have to look closely, because the performers hide it well. It may help to change the video settings to 720p or 1080p and watch in full screen. The easiest way to pick up on the eye blinks is to watch Donald at 3:34 when Minnie says “You mean you don’t believe in dreams?”. Keep your eye on his eyes and his left hand. Every time his eyes close, you can see his hand close. That’s his eye control.

Open hand = open eyes:

Closed hand = closed eyes:

The mouth is the same, but with the right hand. If you watch Mickey during this segment, you can see it if you watch closely. However, since the quick opening and closing would be more obvious, you’ll notice that the characters spend much of the time that they are talking with their right hand behind their back, so the audience doesn’t see them opening and closing their hand as they talk. When their hand isn’t behind their back, they are moving it around to mask the motion.  When Mickey says “dreams come true!” at 4:22, you see his middle finger closing on his hand with each word.

Of course, this show uses pre-recorded dialogue. You could always throw in Disney’s patented Speech Transformation System (patent #5,327,521 - [pdf file]) and have the performer in the costume do the talking.

You may need to be a rocket scientist to fully decode the patent, but the basics of it are that the performer wears a computer (number 12 above). When they speak into a noise-muffling mask (number 18) which keeps their own voice from being very audible outside the character head, a microphone in that mask (number 14) picks up their voice, sending it to the computer to be turned into Mickey’s voice and played through the speaker on Mickey’s chest (number 16).

The patent was filed in 1993 and granted in 1994, and it’s just now becoming feasible to do it on a somewhat regular basis. I’m not sure if technology is just now catching up to the concept, or if it’s just now able to fit inside a costume with a performer.

I probably don’t have to say this but since this is much less widely known than, say, how the Pepper’s Ghost illusion works, I wouldn’t go spouting off this info during the show while you’re in the parks. You may ruin a little kid’s day.