A day with Bowser Jr. Wiki

Hammer Bro is a loyal servant of Bowser.

As such, he performs many tasks, such as guarding the airship from the outside (as seen in First Episode) as well as from the inside (Rise of Fawful), and handling foreign prisoners (Fawful in Rise of Fawful) as well as domestic (Ludwig in Two Koopas for a Throne/Rise of Fawful).