From the Super Mario Wiki
A Drillbit Crab is a crab-like enemy with a drill as a shell found exclusively to Mario & Luigi: Bowser's Inside Story. These enemies are found in Plack Beach. Bowser can simply walk into them to defeat them, gettings five coins in the process, but the Mario Bros. have to battle them head-on, being careful not to use any Jump attacks (due to the drill). In battle, the Drillbit Crab will lean towards the direction of the bro. its going to attack. It may move straight into the bro with its drill. This attack needs to be countered with the Hammer. Failing or neglecting to do this results damage and sometimes the DEF-Down aliment. Its other attack consists of drilling underground and trying to hit a bro. It will then protrude its drill and move sideways, trying to attack both bros. This attack needs to be countered with a jump. Not doing so will cause damage and can also receive the trip status effect.
These enemies may sometimes be paired with Pendrils in battle.
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