This story sketch by Bill Peet inspired Milt Kahl, who aimed this scene featuring Madame Mim, as she temporarily turns herself into an "ugly" creature in front of Wart. Milt used practically everything Peet provided in terms of staging, expression and design.
There are beautiful key moments here that make the scene so successful and satisfying to watch:
Mim completely covers her face with her hair, before she reveals a scary face. There is a a strong squash expression on "B" followed be a stretch for the "OO".