THE CAKE IS A LIE
An Aperture Science Weighted Storage "Companion Cube" is a sentient cube, which is extremely heavy and is decorated with hearts. It was developed by Aperture Science, but a certain dangerously homicidal AI decided to stuff dead people (including the employees, which were killed with neurotoxin) inside the cubes. This led to at least one person (named Doug Rattman, or "The Ratman") being able to converse with the cubes. However, no-one has ever managed to find out what would happen if the cube passed through an emancipation grill, as the one test subject who ever managed to interact with the cubes was not presented with any emancipation grills. The theory is that, since test subjects cannot be emancipated, but cubes can, when a companion cube passes through an emancipation grill, an unconscious test subject or employee will remain. But that's just a theory...
A GAME TH *gunshot*