Boo is a fictional character from the popular video game series Super Mario. He is depicted as a ghost with a round, white body and a large mouth, often characterized by his playful and mischievous nature. Boo typically appears in haunted locations within the games, where he can be seen floating and trying to scare players. In the games, Boo has the ability to become invisible when approached, making him a tricky opponent. He is often accompanied by other ghostly characters and is known for his signature ability to chase players while giggling. Boo has become a beloved character among fans of the Mario franchise.