Robecca has an entirely new body mold all to herself, so I thought I'd point out some of the unique features.
her entire body looks like it has been pieced together from metal plating that has been bolted together. some of her joints, such as her shoulder below, have large flathead screws molded in, to look like they are holding her together. in the center of her chest is a piece of metal that is shaped like a heart.
in addition to the gears on her calves (which you should be able to see on her main review page linked above) her lower leg has another unique feature. thus far, Robecca is the only doll produced without the gap between her toes, which only slightly limits her footwear.
I love all the details Mattel puts into Monster High, especially when they go the extra mile to make a particular doll, like Robecca, special.