Help me to think of original ideas for a screenplay

I am working on a series of movies starring the public domain character of Mr. Wogglebug from the book "The Marvelous Land of Oz" by L. Frank Baum. And the third movie in the series involves him having an adventure with the Frogman from the book "The Lost Princess of Oz" and they become the best of friends by discovering how much they have in common. And the plot involves the Wogglebug and his friend Sylvie helping the Frogman to see and overcome the fact he is not the wisest creature in all the world. And I know most of the basic story beats for it, but I just haven't been able to think of anything to fill them in. I need help in this area.