In bonus feature on the DVD release, Polly Bergen admitted she had misgivings about playing "second banana" to Doris Day. Day was the most popular actress in the world at the time, and Bergen expected her to behave like a diva. However, Bergen admitted to "falling in love" with Day, finding her to be extremely charming, funny, and generous.
The movie that Ellen (Doris Day) describes to Bianca (Polly Bergen) while giving her a massage is My Favorite Wife (1940), of which this is a remake.
Doris Day wrote in her 1975 autobiography that because of her cracked ribs, she was so mummified with tape and bandages under her costumes it was difficult to breathe and painful to laugh.
Doris Day proved what a trouper she was when James Garner accidentally cracked 2 of her ribs (during the massage, when he pulls her off Polly Bergen). Garner wasn't even aware that Day was injured until the next day, when he felt the bandage while putting his arms around her.
The producers scheduled the scene with Doris Day riding through a car wash for the last day of shooting, because they were concerned the detergents used in the car wash might affect Day's complexion. When the shoot went off without a hitch, they admitted their ploy to Day, then used the story in promotional materials for the film.