The most beloved "character" in the Valve
game Portal, it is considered a character in most tenses of the word due to its helpfulness and
aura of friendliness, though it does not talk, and thus cannot threaten to stab you.
The Companion
Cube is only used in one level of the
game, but it leaves a lasting memory and somewhat of a motive for the main character to "
kill" GLaDOS, the antagonist of the
game.
The main character, however, does not seem to have as much of a link or heart felt connection as does most other test subjects of the Apeture Science
Computer-Aided Enrichment Center. This is shown by graphetti drawings on the walls in a hidden room within the level of the Companion
Cube. At the end of the level, the main character is forced to euthanize the Companion
Cube in a pit of fiery liquid metal. After which GLaDOS congratulates the main character and comments that she is the quickest of all test subjects to euthanize the Companion
Cube.
At the end of Portal, the main character finally receives the cake in a brief party in which the Companion Cube is invited and surprisingly shows up.
The Companion Cube is your very best friend in the world, is male, cannot talk (though in the event that it does, Apeture Science strongly disregards listening to any of his suggestions), and is covered in hearts.