For a polyhedron to be classed as Rupert, it must be possible to cut a hole in it that is large enough for an identical polyhedron to pass through. It sounds impossible, but many polyhedra have this property. This repository contains Geogebra and OpenSCAD files relating to Rupert polyhedra.
For more information, see https://samhartburn.co.uk/sh/tag/rupert-polyhedra/.