From the Super Mario Wiki
A Rolling Crate is an item featured in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS / Wii U. Although it is technically a Crate, its effects greatly differ. Once hit, instead of being destroyed and expelling items, the Rolling Crate will begin to travel about on its wheels. It will run over any player in the way, damaging them. Players can stand on top of it as it rolls by, unlike regular Crates. If attacked with enough force, they can be broken open to release items.
Super Smash Bros. Brawl
Super Smash Bros. for Nintendo 3DS / Wii U
Blue indicates exclusive to the Wii U version.
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