The 1956 Original Invasion of the Body Snatchers

Don Siegel adapted Jack Finney's 1955 novel for Allied Artists

Don Siegel's (in Body Snatchers, as director) Invasion of the Body Snatchers was released by Allied Artists in 1956, adapted by Daniel Mainwaring from Jack Finney's 1955 serial-turned-novel The Body Snatchers. Kevin McCarthy played Dr. Miles Bennell, a small-town doctor in the fictional Santa Mira, California, who realizes his patients are being replaced by emotionless duplicates grown from seed pods.

The film was made cheaply and quickly as a genre picture and became one of the most analyzed horror films of the decade. Variety, reviewing the 1978 remake, used the original as its yardstick — and declared the remake had cleared it:

"Invasion of the Body Snatchers validates the entire concept of remakes. This new version of Don Siegel's 1956 cult classic not only matches the original in horrific tone and effect, but exceeds it in both conception and execution." — Variety (1978)

The McCarthyism read was denied by everyone who made it

The standard reading of the 1956 film is that it's about either communist infiltration or McCarthyist conformity — critics have argued it both ways, sometimes simultaneously. The people who made it have consistently refused to endorse either reading.

Siegel, Finney, producer Walter Wanger, and McCarthy all said in interviews that they weren't making a political movie. Siegel allowed that the word "pods" described a type of person he recognized — empty, going-through-the-motions — but insisted that entertainment came first:

"The political reference to Senator McCarthy and totalitarianism was inescapable but I tried not to emphasise it because I feel that motion pictures are primarily to entertain and I did not want to preach." — Don Siegel, Scraps from the Loft (compiled interview)

What Siegel did endorse was the pod as a recognizable human type rather than a political metaphor:

"I think that the world is populated by pods and I wanted to show them. I think so many people have no feeling about cultural things, no feeling of pain, of sorrow." — Don Siegel, Scraps from the Loft (compiled interview)

(Wikipedia, Moria)

Allied Artists forced a framing device onto the ending

Siegel's cut ended with McCarthy on a highway, screaming at the audience that "You're next!" — no resolution, no rescue, no one listening. The studio didn't trust the audience with that.

Allied Artists ordered reshoots in September 1955 and added bookends: Miles Bennell is in a hospital, telling his story to a skeptical doctor. At the end, the doctor hears corroborating evidence, believes him, and calls the FBI. The framing device turns Siegel's open nightmare into a closed case. (Moria)

Siegel hated the addition and said so. Philip Kaufman (in Body Snatchers, as director) knew the history and refused to repeat it — see The Ending (Invasion of the Body Snatchers) for how Kaufman avoided giving his studio the same escape hatch.

Kaufman respected Siegel and cast him as the taxi driver

Kaufman did not approach the 1978 film as a remake in the standard sense. He called it a "new envisioning":

"I thought, 'Well this doesn't have to be a remake as such. It can be a new envisioning that was a variation on a theme'." — Philip Kaufman, Wikipedia citing interview

Kaufman had seen the original on release and had argued about it with friends afterward:

"I saw it when it first came out and I remember discussing it with friends." — Philip Kaufman, It Came From Blog (2019)

He also used the 1978 production to acknowledge the original directly. Siegel plays a taxi driver — already converted — who drops Matthew and Elizabeth at what they think is safety and then calls the police on them. Kevin McCarthy appears earlier in the film as the frantic man pounding on car windows on a San Francisco street, reprising his 1956 role in everything but name. See Kevin McCarthy and Don Siegel Cameos.

Kaufman has been explicit about why the nods mattered to him:

"Too often people rip off films without acknowledging the source." — Philip Kaufman, It Came From Blog (2019)

The 1978 film differs from the 1956 film in four concrete ways

The setting moves from small-town Santa Mira to metropolitan San Francisco. Horror in 1956 came from familiar neighbors acting wrong; horror in 1978 comes from a city of strangers where you never had a baseline. See San Francisco as Setting.

The politics move from implicit-and-disputed to explicit-and-specific. Siegel's film kept its subtext broad enough for McCarthyists and anti-McCarthyists to both read it as theirs. Kaufman's film names its targets: human-potential culture, pop-psychology gurus, the fading of the counterculture. See Themes and Analysis (Invasion of the Body Snatchers).

The horror is shown, not suggested. The 1956 film kept the pods largely off-screen; the 1978 film shows the duplicates forming in real time, skin stretching over cartilage, umbilical strands pulling free.

The ending inverts. The 1956 studio cut restores order in the last scene. The 1978 film ends with Matthew screaming in Nancy's face.

Kevin Thomas called the 1978 film a sequel rather than a remake

"A thoroughly scary success in its own right. Not literally a remake — it's more of a sequel, actually." — Kevin Thomas, Los Angeles Times, cited in Wikipedia

The sequel framing is useful. The 1978 film takes place in a world where the events of 1956 already happened and the warning didn't land — McCarthy's character from the first film is still running down the middle of the road, still yelling, still ignored.