The ability to change shape is an ancient trope of Fantasy, extensively discussed in The Encyclopedia of Fantasy. It is a traditional power of various Supernatural Creatures such as Werewolves (invariably) and traditional Vampires; this entry focuses on sf rationalizations of the theme. A defining quality of shapeshifting is its reversibility: a one-way transformation like an insect's progress from larva to pupa to imago is more properly termed metamorphosis. The tragedy of Robert Louis Stevenson's Dr Jekyll IN Strange Case of Dr Jekyll and Mr Hyde (1886) is that his repeated shape- and Identity-shifting to the Mr Hyde body and persona – at first liberating and invigorating – leads steadily downhill towards the trap of irretrievable metamorphosis.
Very commonly in sf – indeed to the point of Cliché – hostile Aliens possess the Paranoia-enhancing power to shape themselves into any form and pass as human, even as a specific individual. A classic example is the Monster of John W Campbell Jr's "Who Goes There?" (August 1938 Astounding) as by Don A Stuart, whose shapeshifting power is omitted from the 1951 movie adaptation but reinstated in The Thing (1982). Though the Red Dwarf (1988-current) episode "Polymorph" (1989) of course plays the shapeshifting-monster scenario for laughs, its titular creature has one impressively nasty guise. A particular frisson attaches to the concept of an attractive woman able to shapeshift into something nightmarish and deadly, as in Species (1995). Dangerous shapeshifters also appear in the films It Came from Outer Space (1953), I Married a Monster from Outer Space (1958) and Lifeforce (1985).
Further prose treatments include episodes of Ray Bradbury's The Martian Chronicles (coll of linked stories 1950; rev vt The Silver Locusts 1951), Brian Aldiss's "Outside" (January 1955 New Worlds), Leo P Kelley's The Counterfeits (1967) and Gregory Benford's and Gordon Eklund's Find the Changeling (1980). In Darker Than You Think (December 1940 Unknown; exp 1948), Jack Williamson presents a Pariah Elite of shapeshifters who by a fluke of Evolution have split off from and are fated to supplant the human race; the hero's horror at this prospect is muted by the discovery that he too is a member of what will be the winning side.
Many variations on the shapeshifter theme have been devised. In Robert Sheckley's "Keep Your Shape" (November 1953 Galaxy), Earth's huge variety of natural forms (both flora and fauna) proves irresistibly tempting to protean Aliens whose military discipline allows only certain prescribed shapes. Characters absorbed by an alien blob in Damon Knight's "Four in One" (February 1953 Galaxy) find they can modify its amoeba-like body and rebuild it in human form. The menacing-seeming shapeshifter in James White's Sector General story "Visitor at Large" (June 1959 New Worlds) proves to be a frightened child; later episodes of this space-hospital saga feature a benign doctor of the same highly adaptable species. In Clifford D Simak's The Werewolf Principle (1967), a space explorer has undergone Genetic Engineering enabling him to imprint upon and take the form of encountered Aliens, the better to understand them.
Further shapeshifting protagonists are found in Ron Goulart's light-hearted Chameleon Corps series of special-agent stories opening with The Sword Swallower (1968); in the final section of Gene Wolfe's The Fifth Head of Cerberus (fixup 1972), perhaps the subtlest of all sf shapeshifter narratives; in Octavia Butler's Wild Seed (1980); in M A Foster's The Morphodite (1981), whose title character's primary function is as an assassin whose getaway is facilitated by an automatic shift to a new form of opposite sex after each kill; and in K A Applegate's Animorphs sequence, beginning with Animorphs: The Invasion (1996). Various Comics characters have such mutability as their Superpower: for example, Mystique in X-Men. Several shapeshifting species are encountered in the Star Trek universe, including the Changelings of Star Trek: Deep Space Nine, one of whom is the Space Station's security chief.
Terminator 2: Judgment Day (1991) famously deploys a shapeshifting killer Robot; a similarly fluid assassin based on Nanotechnology wreaks havoc on enemies of the Culture in Iain M Banks's Look to Windward (2000). Both may be considered sophisticated descendants of the anthology creature in A Merritt's The Metal Monster (7 August-25 September 1920 Argosy; 1946), which can rearrange its very many metal parts – rather like a Lego set – into variously functional forms.
A restricted but still useful form of shapeshifting is the ability to disguise oneself by relatively minor willed rearrangement of facial features and musculature. Possessors of this talent include the hero of Theodore Sturgeon's The Dreaming Jewels (February 1950 Fantastic Adventures; exp 1950; vt The Synthetic Man 1957), who at one point – though with some pain and difficulty – becomes outwardly a woman; the "Chameleon" Mutants of Eric Frank Russell's Sentinels from Space (November 1951 Startling as "The Star Watchers"; exp 1953; vt Sentinels of Space 1954 dos); the "Tleilaxu Face Dancers" of Frank Herbert's Dune sequence, first introduced in Dune Messiah (July-November 1969 Galaxy; 1969); and the "Changer" protagonist of Iain M Banks's Consider Phlebas (1987).
Even in the Science Fantasy context, shapeshifting has greater credibility when consistent with Physics – specifically, the law of conservation of mass. Thus in Poul Anderson's Operation Chaos (stories 1956-1959 F&SF; coll of linked stories 1971) a were-tiger and a were-fennec (desert fox) are of necessity a grossly large man and a very small one; Mutant shapeshifters in Sheri S Tepper's True Game series, beginning with King's Blood Four (1983), must laboriously ingest extra mass to assume larger-than-human shape; Terry Pratchett's Discworld variation on the traditional vampire/bat transformation in Thud! (2005) sees a woman become an entire flock of bats having equivalent mass. [DRL]
see also: Glen A Larson; Leviathan; Patricia A McKillip; Meet the Applegates; R M Meluch; Society; Élisabeth Vonarburg.
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