Hammer Bros are specialized Koopa Troopas commonly found in pairs (though not exclusively so) who wear light armor and utilize hammers as their main weapons. Hammer Bros. first appear in the later levels of Super Mario Bros..
Hammer Bros are described in various games as being the elite of Bowser's army and often appear in games either as powerful generic enemies or as boss characters. A Hammer Bros.' attack pattern consists of guarding a small area and tossing hammers at the player, occasionally moving around or jumping ; the Mario RPG games introduced a more varied attack pattern for Hammer Bros., such the ability to throw a rapid volley of hammers or throw a single hammer with enough force to literally shrink the player. Beginning with Mario Superstar Baseball, Hammer Bros. appear infrequently as playable characters in spin-off Mario games. They appear in Super Smash Bros. Brawl as Assist Trophies. In Mario Superstar Baseball, They use a hammer as a bat. They also appear as a boss in Mario Party DS and as an unlocked playable character in Mario Party 8.
In The Super Mario Bros. Super Show! and The Adventures of Super Mario Bros. 3 by DIC Entertainment, Hammer Bros. make sparse appearances as antagonists. Printed mediums such as Nintendo Comics System and Nintendo Adventure Books make more frequent use of Hammer Bros. In the Super Mario Bros. 1993 film, a reference to the Hammer Bros. appears in the form of a tattoo parlor known as "Hammer X Bros."; the helmets worn by some of King Koopa's troops in the film are also identical to those adorned by Hammer Bros.
Two Hammer Bros are fought on Mushroom Way as bosses. Mario must fight them alone but fortunately, they are weak to his Jump move. After the Hammer Bros. are defeated by him, Mario is get a Hammer as his first weapon.
Hammer Bro's first appearance in Mario Party was in a mini-game called Hammer Drop, this mini-game was featured in the very first Mario Party. The object of the mini-game was to catch the coins and money bags taken and thrown by Hammer Bro. while at the same time trying to avoid the hammers also thrown by Hammer Bro. In this game everyone won coins.
Hammer Bro's second appearance was in Mario Party 2 in a mini-game called Deep Sea Salvage, the object of this game is almost identical to the mini-game Hammer Drop from Mario Party. The player had to collect coins and money bags thrown by Hammer Bro. while avoiding the hammers, once again also thrown by Hammer Bro. except this game was played in the water instead of on a tower, thus there was no way for the player to go out. In this game everyone won coins.
Mario Party 5 was the first game on the Nintendo GameCube that Hammer Bro made an appearance in. In the game it appeared as a capsule, the capsules effect caused whoever stepped on it to get hit by Hammer Bro's hammers, and lose 10 coins. Hammer Bro also appeared in the mini-game Fight Cards as a referee, where his role was to decide the winner of a round and who would be eliminated.
In Mario Party 7 Hammer Bro appeared as an Orb having the same affect as the capsule in Mario Party 5 except that the owner of the orb would receive the ten coins taken instead of them going to waste. Hammer Bro also appeared in the eight player mini-game Hammer Spammer, where the eight players would have to doge the multiple hammers thrown by the four Hammer Bro's and the two giant hammers that would occasionally drop.
Mario Party 8 is the first game in the Mario Party series that Hammer Bro was made a playable character. He was unlocked by beating the Star battle area on all boards and then VS him on Bowser's board and win. (Note if you VS Blooper you will unlock him not this Koopa.)
Hammer Bro was not playable in Mario Party DS, although he did appear as a boss of Toadette's Music Room. He had two spaces on the board that would send anyone who landed on them flying to another part of the board. To clear the board, Hammer Bro had to be defeated in a mini-game called Hammer Chime, a simple "Simon Says" style game where Hammer Bro would beat any number of five different colored drums and then the player had to copy, and each of the rounds would get harder. There were a total of three rounds. Hammer Bro spoke for the first time in Mario Party DS saying "Yo, yo!".
Hammer Bro appeared in Super Smash Bros. Brawl as an assist trophy, a trophy, and an enemy. As an assist trophy hammer bro. is invincible and will throw hammers all over the stage. In Subspace Emissary, a Hammer Bro. will again throws large hammers at players, but if a player stands too close to a Hammer Bro., Hammer Bro. will hit the player with his head.