Iron ball

Big Steelies (also referred to as Bowling Balls ) are large iron balls 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 final battle with Bowser in Super Mario World (and reappear in its remake). He drops these from his Koopa Clown Car. Mario or Luigi can jump over them to avoid getting hit. Mario or Luigi can also spin jump on them without getting hurt. It can be destroyed if Mario or Luigi uses his sliding cape attack against it using a Cape Feather, but it will show a glitched sprite.

Super Mario 64 / Super Mario 64 DS
In Super Mario 64, they are referred to as iron balls, rolling balls, or simply balls. They appear in Bob-omb Battlefield; Tall, Tall Mountain; and Tiny-Huge Island as an uphill hazard. Several more also appear in the DS remake's Battle Fort. In the remake, Wario has the ability to destroy them by punching or kicking 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, which Mario dodges. 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
Big Steelies are mentioned in Super Smash Bros. Melee in the Koopa Clown Car trophy, known as "bowling balls".

Mario & Luigi: Bowser's Inside Story / Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey
In Mario & Luigi: Bowser's Inside Story, Big Steelies, referred to generically as "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 remake, these are replaced with barrels). Later, Midbus crushes Bowser with a massive one, prompting Mario and Luigi to visit the Arm Center one last time.

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 causes an iron ball to fall onto a random enemy after an "Excellent" rating is achieved.

Other appearances
In Super Mario Maker, graphics for Big Steelies exist unused in the Super Mario Bros. game style's object graphics. The sprite is green instead of dark gray, however.