As we already know, Margaret Hamilton loved playing the Wicked Witch in the movie. She even returned to the role after being severely burnt due to a combination of an inept special effects team and flammable makeup. It was the role that made her career - but she'd played no roles like it beforehand, and there was nothing even vaguely unpleasant about her in real life.
Before accepting the part, Hamilton was struggling to make it as an actor, having to do teaching work on the side to make ends meet. She maintained a strong interest in education after she became famous, advocating for making reading material available to children and even returning to teaching Sunday school classes in the 1950s. She also served for a while on the Beverley Hills Board of Education. She even appeared in 'Mister Rogers Neighborhood' to show that the witch was just a character, and not something to be afraid of.