Mr. Fullerman is a fictional character from the children's book series Mr. Popper's Penguins by Richard and Florence Atwater. He is a kind and imaginative man who works as a house painter. Mr. Fullerman's life changes dramatically when he receives a surprise gift of a penguin, leading to many humorous and adventurous situations. As the story unfolds, Mr. Fullerman becomes a loving caretaker to his penguin, named Captain Cook. He faces challenges as he tries to provide a suitable home for Captain Cook and eventually expands his family of penguins. Mr. Fullerman's character embodies themes of creativity, responsibility, and the joy of unexpected surprises.