Iron Block

Iron Blocks are metal crates found in the New Super Mario Bros. sub-series.

New Super Mario Bros. Wii
Iron Blocks first appear in New Super Mario Bros. Wii. They are characterized as boxes moved by Conveyor Belts, and they are sometimes infinitely spawned by characteristically defined generators. Iron Blocks come in four different variants, all of which are a combination of widths 2-4 and heights 2-4, and getting crushed by a falling Iron Block results in an immediate loss of life. They appear only in, where they are the gimmick of the level.

New Super Mario Bros. U / New Super Luigi U / New Super Mario Bros. U Deluxe
Iron Blocks return in New Super Mario Bros. U and New Super Luigi U, where their behavior is largely unchanged from New Super Mario Bros. Wii. They appear in Roy's Conveyor Castle in the former and in Roy's Ironclad Castle and P Switch Peril in the latter. Additionally, the 4×4 variant features Bowser's emblem on its visible face.

Iron Blocks retain the aforementioned roles in New Super Mario Bros. U Deluxe.