Koopa Shellceiver

From the Super Mario Wiki
The Koopa Shellceiver from Super Princess Peach.

The Koopa Shellceiver is a device that allows the Hammer Bros. to attack something in the game, Super Princess Peach. During the game's intro, a Goomba walks into Peach's Castle with the Vibe Scepter. The Hammer Bro then asks the player to say "all clear", which signals the attack on the castle.