Companion Cube

The Weighted Companion Cube, or Companion Cube, is an item in Valve's Portal games. It first appears in a single level of the original Portal, Test Chamber 17, as one of Aperture Science's ordinary Weighted Storage Cubes with hearts printed on its sides; GLaDOS gives it to Chell, tells her it will be her faithful companion, and after Chell has carried it through the whole chamber forces her to dispose of it in an incinerator. Project lead Kim Swift conceived the cube, drawing on an account of isolated subjects attaching themselves to inanimate objects, and Erik Wolpaw noted that incinerating it taught players the mechanic needed for the final boss battle.

Redesigned Companion Cubes return in Portal 2, and the original is shown to have survived both games as an ending gag. The cube gained a large fan following despite never speaking or acting, was nominated alongside GLaDOS for G4's Best New Character award, and spawned official merchandise including plush toys and fuzzy dice.