blink and you miss it
These Disney Films Contain A Hidden Easter Egg With A Special Message
A fiercely competitive man, Milt Kahl's easter egg was a technique that only he was skilled enough to do and he knew it. Looking back, you've probably also seen this one signature move in a lot of Disney classic movies.
Indeed, how does one hand draw a moving mouth going all directions while also following a script? That's like four different things you gotta animate at once.
Via disneycicerone.