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The Gaddlight as seen from Mario Party 4.

The Gaddlight is one of Professor Elvin Gadd's inventions used in Mario Party 4. When an opponent sent a Boo to steal coins or a Star from another player who had a Gaddlight, they automatically used it to flash light at the Boo, scaring it away. It serves the same function as the Boo Repellent from Mario Party 3.