Mary Katherine Gallagher is a fictional character from the comedy sketch show Saturday Night Live (SNL). Portrayed by Molly Shannon, she is known for her quirky personality, awkwardness, and signature move of dramatically raising her arms and shouting, "Superstar!" The character often finds herself in humorous situations, showcasing her desire for acceptance and fame. Mary Katherine is a Catholic schoolgirl with a vivid imagination, and her antics often involve her crush on boys and her attempts to impress them, making her a memorable and beloved character in SNL history.