Broozer

Broozers are boxing ghosts that first appear in the game New Super Mario Bros.. They have huge grimaces on their faces and are perpetually scowling.

New Super Mario Bros.
In New Super Mario Bros., they are found in two locations: 5-Ghost House and 5-C. Broozers blindly run into the direction of Mario (or Luigi), punching at anything in their way. These enemies can be useful, and they can punch otherwise unbreakable bricks, allowing Mario to reach items and Star Coins that could not otherwise be reached. Mario must jump on a Broozer three times to defeat it. However, a Ground Pound, being hit by Mario doing a Shell Dash, a Fireball or walking through them as Mega Mario can defeat these enemies in one hit, with the latter making the Broozer spinning erratically while falling defeated. Also, because of their bad traction, Broozers often can be forced to fall into gaps in the floor by running past their target and being unable to stop.

New Super Mario Bros. Wii
In New Super Mario Bros. Wii, they appear in World 7's Ghost House. They have the same function as they did in New Super Mario Bros., only this time, in addition to breaking bricks, it can also knock over barrels and cause them to roll down stairs. They are imperative to finding a shortcut to World 7-5, as Mario must lure one to bust open a hidden, unseen door so he can take the secret exit and unlock the level. Although they can be frozen by Ice Mario, Broozers cannot be picked up afterward. Unlike in the first game, where they have a smirk, there is now a frown in this game and every game after.

New Super Mario Bros. U
In New Super Mario Bros. U they appear in two Ghost Houses, the Which-Way Labyrinth in Soda Jungle, and later appear in Spinning Spirit House in Meringue Clouds.

New Super Luigi U
Broozers appear in the level Broozers and Barrels, the first level of Frosted Glacier.

Paper Mario: Sticker Star
Broozers make their Paper Mario series debut in Paper Mario: Sticker Star. Two of them appear in Bowser Jr.'s Flotilla, where they are battled alongside a Boomerang Bro, their only appearance in-game. They attack by hitting barrels into Mario, and floating up to him and punching him. After taking some damage, they will start flailing their arms around, dealing damage to Mario if he tries to attack them up close, therefore preventing Mario to do any direct attacks. The Rampage mode ends in a few turns. Then they revert back to their normal attack pattern. After winning the battle, there is a chance that the player may earn a Barrel stickers.

Mario & Luigi: Paper Jam
Broozers make their Mario & Luigi series debut in Mario & Luigi: Paper Jam. They appear as enemies in Neo Bowser Castle in both normal and paper form.

Trivia

 * Broozer is derived from the word "bruiser" and "Boo", the ghost enemy.