The Hammerhead Bros. are characters that appear in the game Mario & Luigi: Superstar Saga. The Bros. are named Sledge and Mallet and they are responsible for making and upgrading Mario and Luigi's hammers.
Sledge is the oldest of the two Hammerhead Bros. and he has been making hammers for years. His red facial features make him resemble Mario. He is also one of the wisest of the two.
Mallet is the youngest of the two Hammerhead Bros. and has been learning how to perfectly make hammers from his older brother. His green facial features make him resemble Luigi.
The Hammer Bros. earned their name from "Sledge" and "Mallet", respectively, and both terms are used as alternatives for hammers.
The Hammerhead Bros. are first seen in Hoohoo Village where they offer to make hammers for Mario and Luigi. However, they first need Hoohoo Blocks in order to make them and sends Mario and Luigi up Hoohoo Mountain to retrieve some. After Mario and Luigi send down a couple of Hoohoo Blocks, the Hammerhead Bros. use their technique to make some hammers for Mario and Luigi.
The Hammerhead Bros. are seen again near Beanbean Castle Town where they have move their workshop to further their hammer making. They also revealed to Mario and Luigi that they can now upgrade their hammers to break down harder rocks.