An imitation is a Thing which has perfectly assumed the form of a victim. Imitation creatures first appeared in the short-story Who Goes There?, which forms the basis for John Carpenter's 1982 film The Thing. The mode of assimilating other life-forms has been a staple across the film, literary and video-game series. They are the most common types of Thing that's encountered throughout the series.
An imitation perfectly copies its assimilated victim's form; replicating all that the host possessed, such as internal/external physical appearance, mannerisms, voice, and even physical disorders. When threatened or preparing to assimilate another organism, the creature violently bursts open and attacks with a variety of strange and terrifying assemblages - often taken from previously assimilated anatomy. Every part of the imitation (even down to the cellular level) is an individual organism and possesses an instinctive desire to survive. Consequently, when faced with insurmountable odds, an imitation is capable splitting into multiple, albeit smaller, creatures formed from the severed body parts of the whole. Primarily intent on remaining hidden, the imitation's only concern is for its own self-preservation, and will even allow its own kind to be destroyed without remorse as seen in the case of Palmer and Norris.
The film, literary and video-game series has outlined several methods of distinguishing an imitation from an original creature, based around either blood-testing or searching for missing inorganic components (for example, tooth fillings or prosthetics). Blood tests work by coercing autonomous Thing cells (imitating blood cells) to act in self-preservation - for example, crawling away from a hot needle. Another blood test variant is the blood serum test, where a suspected imitation's blood is mixed with uncontaminated blood; which will hypothetically react if the creature is an imposter. The 2002 video-game, The Thing, adds a further method of testing in the blood test hypo - a portable blood testing device which exposes a suspect's blood to a caustic chemical agent. Once exposed, the creature will invariably attempt to defend itself, mutating various appendages for the task. Like any of the Thing's forms, incineration is required in order to completely kill it. Utilizing explosives or delivering powerful electric shocks are also effective (especially in the original short story).
- Treatment of the creature's ability to imitate has varied across the film, literary and video-game series. Unlike the film series, where the Thing is unable to replicate inorganic matter, the 2002 video-game explicitly presents the Thing as a 'virus', which has the ability to replicate the original biological entity, including their clothing. The Dark Horse comic series features almost instantaneous assimilation by touch (even through thick clothing in the case of Pybus). The 1993 comic Eternal Vows even grants the creature the ability to swap its appearance with victims.