The Hammer Brothers made their first appearance in Super Mario Bros., kicking off 20-plus years of confusion on how they should be called since it’s a type of Koopa and not related to an actual family. These Koopas have three purposes in life: jumping, throwing hammers, and introducing anxiety to small children.
In the original game, the helmet-wearing Koopas usually appear in pairs and litter the screen with raining hammers. Unlike most enemies which had a distinct pattern that could be easily dealt with, the Hammer Brothers moved erratically between rows of blocks which meant that running past them was a risky proposition without a star or fire flower power-up. They would even start to chase Mario if they remained on screen for too long.