WHY WERE THEIR FACE-CHEEKS FLAPPING???

In the episode where Clarence and Chad go 'camping' and they run into that father and son in the woods, what was up with their faces? How do you come up with that?? Chad's reaction was just like I would've reacted as well. i wouldn't be able to stop staring and I'd be very weirded out though I'd feel bad for feeling that way. But WHY were they jiggling??? LOL