Hollywood legend claims that, during the filming of Rock Hudson and Doris Day's bathing suit scene (set on a soundstage beach) one of Hudson's testicles kept popping out from his swim trunks. While screening dailies the next afternoon, the crew laughed so hard, they became teary-eyed, especially when the projectionist figured how to roll the film back-and-forth so it looked like Hudson's testicle was doing a "dance."

The colors of the smoke in the explosions in Dr. Tyler's chemical laboratory correspond to the ultimate colors of the candy wrappers on the final VIP product.

About a year and a half after completing this film, its twice Oscar-nominated costume designer Irene committed suicide by jumping off the roof of Hollywood's Knickerbocker Hotel. Doris Day, in her 1975 autobiography, suggested the suicide of Irene may have been motivated by the designer's secret, unrequited love for Gary Cooper and Cooper's then recent death from cancer.

All close-up shots of Doris Day are in soft focus.

Donna Douglas was cast as Tony Randall's secretary shortly before landing the role for which she is best-remembered: Jed Clampett's daughter Ellie Mae in the long-running CBS sitcom, The Beverly Hillbillies (1962). As the screenplay was co-written by "Hillbillies" creator Paul Henning; it's a pretty safe bet he remembered her when casting the role.

Continuity

When Carol goes through "Linus's" wallet and discovers he is actually Jerry Webster, she is holding a blue nightgown. When she turns around to march into his room, the nightgown disappears.

The entire movie takes place during the one week the VIP's Greek chorus is in town, yet during that week, Webster and Ramsay go on vacation and grow beards that would take at least three weeks to grow.

Carol and Jerry are seen running out of the ocean towards a blanket and two beach chairs. After toweling off, they start to recline on the chairs. Jerry lies down with his head propped up against the back of his chair, his shoulders at the top edge of the blanket, and Carol starts to recline in a similar position. The next shot, from overhead, finishes the action of Carol lying down except now she is slightly further away from her chair, and she lies down flat with her head on the blanket. Jerry is now also suddenly further down on the blanket, lying flat with his head on the blanket instead of his chair.

When Webster and Ramsey are eating together, Webster drinks coffee from a cup. Next shot, he is still moving the cup to his mouth.



Factual errors

Jerry and Rebel both wrongly pronounce the Latin phrase, and the English subtitles misspell one word. The phrase should be Veritas et probitas super omnia. Both characters clearly drop the "p" and say instead, "robitas" which isn't a word.



Revealing mistakes

None of the stamps on the letters that come into the agency regarding VIP have been canceled.

When Peter Ramsey goes to the laboratory to check on the progress of VIP for the last time, he closes his eyes and winces just before the purple smoke appears. He obviously knew it was coming.

At one point in the film, Jerry and Carol talk with an aquarium behind them, which holds a fish that is eaten by another as the scene ends. The "aquarium" is clearly just a short loop of film being played forwards and backwards in succession - the fish repeats the same two motions over and over until it is eaten.



Audio/visual unsynchronized

When Carol meets Mr Miller for the first time after the big party, he's hung over and playing a bass. It is obvious that he's not actually playing it. Although we hear different notes being played, his left hand never moves and his right hand doesn't always match the rhythm.



Errors in geography

Miller drunkenly tells Carol that he's flying from New York back to Richmond, "just passing over Pittsburgh." Not even close.

When Rebel testifies before the Ad Council, she says Jerry considers the top of the Chrysler Building "Inspiration Point", because "it looks down on Madison Ave." The Chrysler Building looks down on Lexington Ave and because of buildings in the way, Madison Ave, two blocks away, is not clearly visible.



Plot holes

Carol says that even a glass of champagne will cause her to get drunk due to her low tolerance. Yet right before she finds out that her house guest is actually Jerry Webster, she drinks a glass of champagne. However she never feels any effects of the alcohol while she drives 30 miles to the beach and back.



Boom mic visible

The shadow of the book mike is visible on the back of Carol Templeton's office chair.



Character error

The liquor industry representatives approaching Webster about VIP's formula instead of Tyler makes no sense.