Sentry Beam

Sentry Beams are metallic robots that appear in Super Mario Galaxy and its sequel, Super Mario Galaxy 2. They are invulnerable enemies that attack by firing lasers from their mouths at Mario or Luigi.

Super Mario Galaxy
Sentry Beams debut in Super Mario Galaxy, first appearing in the Battlerock Galaxy. They also appear in Bowser Jr.'s Airship Armada and the Toy Time Galaxy. Sentry Beams are stationary robots that hover in place, firing a laser at Mario or Luigi if he approaches them. They cannot be destroyed by any means, but if Mario or Luigi stands on top of them, they cease all motion until he gets off and starts to move again.

Super Mario Galaxy 2
Sentry Beams reappear in Super Mario Galaxy 2, and they are encountered only in the Mario Squared Galaxy and the Grandmaster Galaxy. They behave identically to their first appearance.