Clampy

Clampies (also known as Giant Clams or simply Clams ) are giant, purple Clam enemies that first appeared in New Super Mario Bros. Wii.

New Super Mario Bros. Wii
Clampies first debuted in New Super Mario Bros. Wii, only appearing in World 1-4 and in a secret area in World 4-1. They trap a character in its shell if it closes on a character, causing them to take damage and then opening back up. Most Clampies have Coins in their valves in order to lure a character close so they can attack them.

New Super Mario Bros. U
Clampies also appear in New Super Mario Bros. U where they act exactly like they do in New Super Mario Bros. Wii. They are very rare and only one can be found in a secret area of Waterspout Beach. They are also found in World Coin-5.

Mario Kart 7
Clampies appear in the Cheep Cheep Lagoon and Daisy Cruiser racecourses in Mario Kart 7 for the Nintendo 3DS. They are obstacles that are found only underwater, and like in New Super Mario Bros. Wii, they have Coins and Item Boxes between their valves that racers can pick up, taking care of not being trapped by the Clampy's valves.

Mario Party 10
Clampies reappear in Mario Party 10 in the board Whimsical Waters. They also appear in the minigame Cheep Cheep Check, where they serve as distractions for the group players.