Nattō (ナットー) is one of the hypothetical new enemies that Mario encounters in Super Mario-kun volume 1, in a chapter dedicated to the possibilities in a "Super Mario Bros. 5". It is a Buzzy Beetle with nattō on its shell, making it as sticky as the aforementioned food. Its name is a reference to the Buzzy Beetle's Japanese name,「メット」(Metto), which is written similarly.
Mario and his friends encounter it underground, where the former gets stuck in the Nattō's shell. Yoshi then jumps in and eats it, saving Mario.