Hammer Bros. are enemies and are one of the original characters in the game Super Mario Bros. for the Nintendo Entertainment System. The enemy usually come in pairs of two, and they will constantly throw hammers at Mario and Luigi. They are counted as the hardest enemy other than Bowser to defeat.
They have appeared in Super Mario Galaxy 2 as 3-D enemies and they are in most of the Mario sidescrollers, such as Super Mario Bros. 3 and New Super Mario Bros. and Dance Dance Revolution: Mario Mix, guarding the gate to the amusement park. They've also appeared as a playable character in the game Mario Superstar Baseball, on Bowser's team and in Mario Strikers Charged as an offensive sidekick, a character that is good at passing and shooting. They also appear as an assist trophy in Super Smash Bros. Brawl. Also, in Mario & Luigi: Partners in Time, After the adults were taken away, Baby Mario and Baby Luigi were left to fight a pair of Shroob-[brain]washed Hammer Bros. Upon being defeated, they were freed from the Shroobs' control, and gave the Baby Bros. hammers as thanks.
Mario Party Series
Hammer Bro. is a playable character in Mario Party 8, but he has to be unlocked first. A Hammer Bro. is also an enemy in Mario Party 7. He is also the boss of Toadette's Music Room in Mario Party DS.