Leonardo is terrible at being a monster. No matter how hard he tries, he can't seem to frighten anyone. Determined to succeed, Leonardo devotes his time to becoming a scary monster. Finally, he finds a nervous little boy and scares the tuna salad out of him. However, scaring people isn't quite as satisfying as he thought it would be. Leonardo decides he wants to be a good friend instead of a terrible, awful monster. Based on the children's book by Mo Willems.