From the Super Mario Wiki
The Gray Magikoopa is a special kind of Magikoopa that first appeared in Paper Mario, but are abbreviated as GRY Magikoopa in the game. The Gray Magikoopas can turn allies invisible. They sometimes ride brooms in battle, which allows them to hover above the ground and cause hammer attacks to miss. Said brooms will disappear if the rider is hit with an attack, though. Like all Magikoopas, they duplicate themselves or run away if alone in battle.
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