Production designer Ted Haworth came up with a fairly simple and inexpensive (about $30,000 total) idea for creating the pods. The most difficult part was when the pods burst open, revealing the likenesses of the actors. The actors had to have naked impressions of themselves made out of thin, skin-tight latex. Making the casts, which involved being submerged in the very hot casting material with only a straw in their mouths to breathe through, was grueling for the actors, especially Carolyn Jones, who was claustrophobic. Dana Wynter recalled, "I was in this thing while it hardened, and of course it got rather warm! I was breathing through straws or something quite bizarre, and the rest of me was encased, it was like a sarcophagus. The guys who were making it tapped on the back of the thing and said, 'Dana, listen, we won't be long, we're just off for lunch [laughs]!' In the end, we had to be covered except for just the nostrils and I think a little aperture for the mouth."
During its original release, papier-mâché pods were on display in theater lobbies, as well as black-and-white cutouts of Kevin McCarthy and Dana Wynter running frantically away from a crowd of pod people.
The film's action required leading man Kevin McCarthy to run for days on end. In numerous scenes, his character sprints for dear life over every possible terrain. "I got charleyhorses [cramps]," admitted McCarthy. Just before the film draws to a close, Dr. Bennell runs through traffic in a panicked frenzy, screaming, "They're here already! You're next! You're next!" Since the exhausted actor hadn't been sleeping well, Don Siegel told his stunt drivers to remain extra alert in case McCarthy tripped without warning. "I was terrified that his timing would be off and he might fall down under the wheel of the cars and trucks," Siegel admitted.
In 1994 this film was selected for preservation in the US National Film Registry by The Library of Congress as being "culturally, historically, or aesthetically significant."
Kevin McCarthy was a good friend of Montgomery Clift but was jealous because in 1956, while Clift was at MGM shooting the prestige big-budget historical extravaganza, L'arbre de vie (1957) with Elizabeth Taylor as his co-star, McCarthy was making this "B"-budgeted science-fiction movie at a cheap studio. Little did either of them know that eventually "Raintree County" would be virtually forgotten and "Invasion of the Body Snatchers" would be acknowledged as a classic.