This is a hard question for most students to answer—again, you don’t want to talk too much about that character, historical figure, or creative work, but instead, describe their influence on you. Perhaps a building’s unique design influenced your desire to study architecture. Maybe a lead character’s actions in a movie or novel oddly paralleled your own actions. Note: If you’re going to write about a fictional character, avoid very common novels that most students read in high school, and instead use a novel that you read independently—it’ll help you stand out.
Not just humor, but the overall tone of your application essay is remarkably important. It's also difficult to get right. When you are asked to write about your accomplishments, those 750 words on how great you are can make you sound like a braggart. Be careful to balance your pride in your achievements with humility and generosity towards others. You also want to avoid sounding like a whiner -- use your essay to show off your skills, not to explain the injustices that lead to your low math score or failure to graduate #1 in your class.