Well, in the Mighty Book story, Mona Lisa's smile could have been influenced by a variety of factors. Maybe it was a moment of pure joy, or it could have been related to a hidden meaning or symbol within the story.
It's hard to say exactly how Mona Lisa got her smile in the Mighty Book. It could be that it was a combination of her inner thoughts and emotions, or perhaps it was something external that triggered it. We might need to explore the details of the story further to figure it out.