However, in the comic Portal 2: Lab Rat, Doug Rattman's Companion Cube is shown speaking to him, possibly as part of a schizophrenic hallucination.

The Companion Cube was initially conceived as part of the gameplay of Test Chamber 17, due to players constantly forgetting to bring the crate along with them.

However, the developers were seeking a way to make the player familiar with how Aperture Science's incinerators worked in order to use them to destroy the personality cores in the final battle against GLaDOS.

Respawn: Gamers, Hackers, and Technogenic Life compares the fact that it must be "euthanized" for the sake of progress to real-world animal testing, especially because GLaDOS implies that it may or may not be sentient.

They further noted that Doug Rattman's scrawls warned Chell that she was the Companion Cube herself, a form of disposable tool utilized by the player to progress through the game.

Others attempted to exploit or glitch the game in order to escape the test chamber with the Cube, such as jamming the doors with security cameras so that the player could leave the room despite not having incinerated it.

[12] Matt Margini of Kill Screen compared the Companion Cube to other video game sidekicks that must be escorted through levels, calling it both an object of "annoyance" as well as "disproportionate emotional investment".

[8] World of Warcraft featured an Easter egg based on the Companion Cube outside of Stormwind, during the game's 2008 "Love is in the Air" Valentine's Day festivities.

[14] Fan Magnus Persson created a fully functioning Companion Cube PC, which Wired called "a triumph" in reference to "Still Alive".