Complex sentence: The Mini Mushroom is a small blue mushroom, a recurring item in the "New Super Mario Bros." series, which shrinks Mario into miniature size, allowing him access areas and pipes that Mario normally cannot reach.
Split into simpler sentences: The Mini Mushroom is a small blue mushroom that shrinks Mario into miniature size. It is a recurring item in the "New Super Mario Bros." series that lets him access areas and pipes that Mario normally cannot reach.