Iron ball

Iron balls, also referred to as Big Steelies, Bowling Balls (also uncapitalized as bowling balls), giant steel balls, and big rollers, are large obstacles that debut in Super Mario World as a final boss attack and return in Super Mario 64 as an uphill hazard.

Super Mario World / Super Mario World: Super Mario Advance 2
Big Steelies first appear in the second phase of the final battle with Bowser in Super Mario World (and reappear in its reissue). Bowser drops Big Steelies from his Koopa Clown Car, and Mario or Luigi can jump over them to avoid getting hit. Mario or Luigi can also spin-jump on them without getting hurt. A Big Steely can be destroyed if Mario or Luigi uses his sliding cape attack against it using a Cape Feather; however, a glitched sprite is displayed if this happens.

Super Mario 64 / Super Mario 64 DS
In Super Mario 64 and Super Mario 64 DS, iron balls are also referred to as rolling balls, cannonballs, or simply balls. They appear on the Bob-omb Battlefield; Tall, Tall Mountain; and Tiny-Huge Island as an uphill hazard. Several more also appear in the DS version's Battle Fort. In the remake, Wario has the ability to destroy iron balls by punching or kicking them, and players equipped with a mushroom can destroy them simply by walking into them.

Super Mario World television series
In the Super Mario World episode "Send in the Clown," King Koopa attempts to defeat Mario in one scene by dropping a Big Steely on him, but Mario dodges it. King Koopa, with the same method, is shown dropping a Big Steely after Yoshi hits him with his Mechakoopas. Mario, however, uses a golf club and knocks the Big Steely at him.

Super Smash Bros. Melee
Iron balls are mentioned in Super Smash Bros. Melee in the Koopa Clown Car trophy, where they are described as "bowling balls."

Mario & Luigi: Superstar Saga / Mario & Luigi: Superstar Saga + Bowser's Minions
In Mario & Luigi: Superstar Saga, an iron ball (called a "rock") appears during the Jellyfish Sisters' tutorial on Dashing, where it must be pushed with the ability. Later, some appear around Gwarhar Lagoon's exterior in timed courses involving the Dash.

Mario & Luigi: Bowser's Inside Story / Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey
In Mario & Luigi: Bowser's Inside Story, iron balls appear in multiple locations. In Cavi Cape, Bowser must punch a falling one in order to knock it into a button; in the game's remake, these are replaced with barrels. Later, Midbus crushes Bowser with a massive iron ball, prompting Mario and Luigi to visit the Arm Center one last time. At Blubble Lake, Bowser can punch some found on spinning mechanisms to push himself into the lake.

Mario & Luigi: Dream Team / Mario & Luigi: Paper Jam
There are Hammers called the Iron Ball Hammer and Iron Ball Hammer DX in Mario & Luigi: Dream Team and Mario & Luigi: Paper Jam, which sometimes cause an iron ball to fall onto a random enemy after an "Excellent" rating is achieved. In the former game, they have a studded appearance, though they are smooth in the latter. The latter game also has them appear in the mission Hammer, Bros!, where they are referred to in localizations as cannonballs.

Other appearances
In Super Mario Maker, graphics for iron balls exist unused in the Super Mario Bros. game style's object graphics. However, the iron ball's sprite is green instead of dark gray, making it resemble the Big Bubble from Super Mario World.