Marianne Thornberry is a fictional character from the animated television series The Magic School Bus. She is known for her intelligence and curiosity, often participating in the adventures led by Ms. Frizzle. Marianne is depicted as a supportive friend who enjoys learning about science and the world around her. In the series, Marianne's character helps to illustrate the importance of teamwork and exploration. Her interactions with other characters, such as Arnold Perlstein and Phoebe Terese, highlight the value of friendship and collaboration in overcoming challenges during their educational journeys.