The Beautiful Geometry of Soap

The Shape Japer can transform into any shape, including the whatchama-hedron you mentioned (although more complex shapes are more difficult as they require more mental calculation and energy to maintain). As much as they would like to, her three-dimensional body only has the capacity to transform into three-dimensional shapes, so she can't transform into four-dimensional shapes such as a tesseract. She also cannot properly transform into shapes with holes in them, such as tori, because homeomorphism something something. They'd probably lose an eye if they tried.

3D shapes yeee

Y2K 3D Aesthetic Shapes Collection by LarysaZabrotskaya