From the Super Mario Wiki
Tox Boxes are recurring enemies in the Mario Series. They are a species of Thwomp that resemble metal or stone boxes with a face on three sides that manage to roll themselves along set paths. The paths they go on are usually similar to their width, making it nearly impossible for Mario to walk around. Tox Boxes first appear in Super Mario 64.
Tox Boxes have faces on all but one side; the last side is only a square hole. This hole is for Mario to stand in as the Tox Box passes over the tile he's standing on, thus letting him survive without being crushed. However, it is still possible to be crushed by the side with the hole if Mario or Luigi stands at the side of a tile when the Tox Box rolls over him.
Super Mario series
Super Mario 64
Tox Boxes appear in Shifting Sand Land, the 8th course of the game. They attempt to flatten Mario by rolling over him. The path is a small maze of tiles surrounded by darker, faster-moving quicksand that sucks Mario in instantly. The tiled maze that the Tox Boxes travel on has a few Red Coins on it, as well as the course's only cannon. If Mario gets squished by a Tox Box's side, he loses three wedges of health.
In Super Mario 64 DS, if Wario is inside one of them and punches (or jumps), the Tox Box will fly somewhere into the sand and sink, unless it falls in the sand that the characters can normally stand in. If this happens, it simply stays in one spot until the player leaves the level. Tox Boxes also appear in the Super Mario 64 DS minigame Tox Box Shuffle, where three of them each hide a Yoshi or a Light Blue Yoshi and the player must guess which Box the Green or Light Blue Yoshi is in.
Super Mario Galaxy
Tox Boxes reappear in Super Mario Galaxy. These redesigned boxes usually appear alongside Thwomps. They only appear in the Beach Bowl Galaxy and the Toy Time Galaxy. In both Galaxies they appear on small pathways, much like they did in Shifting Sand Land.
Unlike the Tox Boxes in Super Mario 64, these ones resemble Thwomps; instead of having the faces spray-painted on, they are carved in a way resembling a Thwomp's face. These Tox Boxes also lack a face on the side opposite the hole. The hole itself has also been expanded quite a bit, and colored in red to resemble a mouth. Also, coming into contact with any of the Tox Box's sides from the outside is considered as being crushed and thus results in an instant death. Their faces resemble the Thwack's expressions.
Super Mario Galaxy 2
In Super Mario Galaxy 2, Tox Boxes reappear in the Stone Cyclone Galaxy, which is basically a remake of the Cyclone Stone in Super Mario Galaxy, but they move faster than they did in the previous game.
Mario Party: Island Tour
Tox Boxes appear in the minigame Hide 'n' Splat in Mario Party: Island Tour. Here they try to squish the players using the same methods as in past games, but get faster as the time limit decreases. They retain their appearance from the Super Mario Galaxy games.
A Tox Box makes an appearance in volume 16 of the Super Mario-Kun. It is an obstacle against Mario's path to retrieve his lost hat from Klepto. Hatless, Mario tries using a Exclamation Mark Block to combat against the Tox Box; he still ends up getting smashed. In the manga, the Tox Box is able to smash Mario, even on the safe side.
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