The main characters in the story are:
* Flora Belle Buckman: A young girl who loves comic books and superheroes.
* Ulysses: A squirrel who is struck by lightning and develops superpowers.
* William Buckman: Flora's dad, who is struggling to write a novel.
* Phyllis Buckman: Flora's mom, who is trying to help her husband and cope with her daughter's obsession with superheroes.
There is no character named Mr. Klaus in the book.