All of the 9-foot-tall Kanamits are played by the same actor - 7'2" tall Richard Kiel. This is most apparent at the end, when two identical Kanamits stand near the spaceship in a split screen effect.
Damon Knight's short story "To Serve Man" first appeared in the November 1950 issue of Galaxy Science Fiction and has been reprinted a number of times, including in Frontiers in Space (1955), Far Out (1961), and The Best of Damon Knight (1976). It was awarded the 1951 "Retro" Hugo Award for Best Short Story in 2001.
The newspaper that Patty picks up is the actual June 14, 1961, edition of "The Los Angeles Times." The top-most headline reads; "Specialist Checks John F. Kennedy's Back." The main banner headline reads; "4-HOUR POWER OUTAGE BRINGS CHAOS TO N.Y.," which refers to the previous evening's power failure in New York City.
In the source story, the aliens are short and look like hairy pigs that walk upright, and go by the name Kanamit (singular: Kanama). In this televised version they're called Kanamits (singular: Kanamit), and they all look like Richard Kiel, wearing a prosthetic "big brain."
The voice-over on the Kanamit spaceship is Joseph Ruskin, who played the Genie in The Man in the Bottle (1960).