During the battle against the Straw Hat Pirates, Moria demonstrates that by manipulating a person's shadow, he can force their physical body to change its shape as well.
Gecko Moria & Oars vs. the Straw Hat Pirates. Plot Highlights: One Piece Episode 371
Chopper deduces that Oars originally died from frostbite 500 years ago in the Land of Ice. During the battle against the Straw Hat Pirates,
Moria systematically takes down several Straw Hats, including Nico Robin, Sanji, and Chopper. Plot Highlights: Chopper deduces that Oars originally died
"Moria Destroys the Straw Hats One After Another!" (or "My Name is Moria!")
Moria also uses a useful defensive feature of his Shadow-Shadow Fruit powers to instantly switch places with his shadow, Doppelman , allowing him to evade attacks—such as when he rendered Nico Robin's Clutch attack useless by swapping locations with his shadow. Episode Overview
Moria uses this "feature" to make the giant zombie, Oars, stretch his limbs just like Luffy. Normally, Oars is a giant who cannot stretch, but Moria extends Oars' shadow, which forces Oars' physical body to elongate to match the shadow's shape.