The woman who answers Uhura and Chekov when they are looking for the nuclear vessel was Layla Sarakalo, an extra who had never acted before and was not supposed to speak much. Sarakalo happened to be on the set when her car was towed away to make room for the film's production. She then offered to be an extra, because she needed the money to get her car back. She was told to "act naturally", and when she was asked, she improvised an answer. Much to her surprise, her unscripted line was kept in the film. This was because director Leonard Nimoy enjoyed the spontaneity of the scene so much that he left it the way it was.
As the alien probe approaches Earth at the film's beginning, it emits a sound wave that Spock determines to be an attempt to communicate with humpback whales. After the first test screening and at the suggestion of Harve Bennett, Paramount Pictures studio heads sent Leonard Nimoy a memo asking him to create an on-screen subtitle to translate the sound, and suggested "Where are you?". Nimoy and Nicholas Meyer insisted that any explanation of what the probe and the whales were saying would ruin the sense of mystery. Eventually, Nimoy convinced Paramount Studios to not use subtitles.
Scotty helps Dr. Nichols "invent" transparent aluminum, which, in real life, became possible 23 years later in 2009, developed partially by Professor Justin Wark of Oxford University's Department of Physics. Oddly enough, it was the year when the franchise was rebooted in Star Trek (2009).
The idea of having Spock give the Vulcan nerve pinch to the punk rocker was inspired by Leonard Nimoy who was walking down the street in New York City, when a punk came out of a store with his boombox blaring, disturbing everyone around him. Annoyed, Nimoy thought "If I was REALLY Spock, I'd pinch his brains out!" (According to Nimoy in the Blu-ray audio commentary).
Kirk R. Thatcher: An associate producer plays the punk on the bus who is nerve pinched by Spock. Thatcher expressed displeasure at the music chosen for his boom box, and asked to write and perform a song that he feel would be more representative of his character. The result was the song "I Hate You".
Majel Barrett, Grace Lee Whitney: There are brief appearances of Christine Chapel and Janice Rand, beloved Star Trek (1966) supporting characters, at Starfleet Headquarters during the alien probe's arrival.
Jane Wiedlin: The Go-Go's rhythm guitarist appears as a communications officer on a starship rendered powerless by the Probe. She is seen on the right of three huge video screens amid a chaotic control room on Earth. Her line: "The condition remains the same. The Probe has neutralized all power supplies. We are functioning on reserves only."
Vijay Amritraj: Captain of the U.S.S. Yorktown was played by a professional tennis player and television commentator who at the time was attempting to transition into an acting career. He is one of three actors from India to appear in the Star Trek franchise. Others include: Persis Khambatta, Ilia from Star Trek: The Motion Picture (1979); Padma Lakshmi from Precious Cargo (2002).
Harve Bennett: The masked surgeon set to operate on Chekov is believed to be the producer, but this is unconfirmed.
Leonard Nimoy: In addition to his role as Spock, Nimoy also played a visitor to Mercy Hospital. This was reportedly an unintentional cameo appearance as he was on the set as the film's director.