The French title "Les Petits Mouchoirs" refers to an idiomatic expression that is similar to the English term "Sweeping something under the rug". You cover something up with a napkin or a handkerchief and pretend it's no longer there even though everyone knows it is. The English term "Little White Lies" is a similar if not identical concept.
The film was France's highest-grossing film in 2010, with more than 5 million tickets sold.
To get the cast used to each other - and to convey a lifetime of friendship - they all lived together for 3 days in the house used in the film.
After seeing Tell No One (2006), Jean Dujardin called Guillaume Canet and told him he really wanted to be part of his next film. Canet - a lifelong friend of Dujardin - was delighted even though the part he had in mind for him was actually a very small one.
The movie that Eric and Marie are watching is Scarecrow (1973), with Al Pacino and Gene Hackman.