A Digga is a yellow drilling enemy that resembles a Bullet Bill. They drill with their bodies exposed on the surface of the ground, which can harm the player if they land in one's path. They first appear in Super Mario Galaxy 2.
Diggas reappear in Lets-a-go, Mario as enemies yet again. They attack in the same way as before, except when they reach a hole or wall, they dig downward or upward, respectively.
There's an orange variant, called a Dig-Digga, which actively pursues the heroes, rather than going in a single direction.