Fred Astaire's character is based on photographer Richard Avedon. In fact, it is Avedon who set up most of the photography for this film, including the famous face portrait of Audrey Hepburn unveiled during the dark room sequence.
The soggy weather played havoc with the shooting of the wedding dress dance scene. Fred Astaire and Audrey Hepburn were continually slipping in the muddy and slippery grass. Hepburn sings several songs. Her next full musical, My Fair Lady, would see her voice overdubbed, much to her disappointment.
Audrey Hepburn did not want to be separated from her husband Mel Ferrer, so filming of the Paris scenes was timed to coincide with Ferrer's filming of Elena and Her Men (USA title: "Paris Does Strange Things") with Ingrid Bergman. Paris' unseasonably rainy weather had to be worked into the script, particularly during the balloons photo shoot scene. During filming of the Paris scenes, much of the crew and cast were on edge because of riots and political violence that were gripping the city.
Fred Astaire also starred in the original 1927 Broadway version of "Funny Face" with his sister Adele Astaire. However, the storylines of the play and movie are entirely different; the film only uses some of the play's songs. Coincidentally, the exact same thing had occurred earlier with The Band Wagon, which had also starred both Astaire and his sister on Broadway in 1931; the film had a different storyline but used some of the play's songs. The only opportunity Astaire had to recreate a role he originated on Broadway was in The Gay Divorce, from Broadway's "Gay Divorce".
The plot of this movie is actually that of Leonard Gershe's unsuccessful Broadway musical "Wedding Bells" - apparently the studio bought the rights to the title just so they could use the song. The original plot of the musical was scrapped, and Gershwin songs from other musicals replaced several numbers originally written by Gershe himself for "Wedding Bells". These numbers were tweaked so that they could fit into the main storyline, and one of them - of course - was "Funny Face". The studio may have felt that the original plot of "Funny Face" could not be properly adapted into a movie as it was an "ensemble" musical with people dropping out and parts changing all the time.
Much has been written about the crew having to contend with rainy weather in Paris during production. For a comparison of how the film might have looked if the sun hadn't appeared from time to time, compare the "Bonjour, Paris!" number from the film - mostly shot in brilliant sunshine - with alternate footage shot on a rainy day that is featured in the trailer.
The little white car that Dick and Maggie drive to the beatnik club is called a VELAM Isetta. They were made between 1955 and 1958. VELAM (Vehicule Leger a Moteur [light vehicle with motor]) was a French company. The French nicknamed the car the "yoghurt pot" because of its looks. It was also known as the "bubblecar", "rolling egg", "little egg" and even "trouser fly" since you could get into the car from the front.
The term 'Empathicalism' is mistranslated as 'Enfaticalismo' ('Emphathicalism') in the Spanish (Spain) dubbed version of the film, making the connection between 'empathy' and the name of invented philosophy completely absurd when it gets explained during the movie.