The Weighted Companion Cube (often referred to as the Companion Cube) is a recurring object and pseudo-character in the Portal universe. It appears almost identical to the Weighted Storage Cube but with a pink heart replacing the Aperture Science logo.
In Portal, the Companion Cube was given to Chell in order to aid her in completing Test Chamber 17. In order to progress through the exit at the end of the chamber, the cube was dropped into the incinerator to be "euthanized". Can't make any noise