Girl In His Pocket (1957)

Starring Jean Marais, Genevieve Page, Jean-Claude Brialy, Agnes Laurent, Jean-Paul Moulinot
Directed by Pierre Kast
(actor & director credits courtesy IMDB.com)

A scientist develops a formula for shrinking living creatures into tiny immobile statues, and ends up using the formula to facilitate an affair with his beautiful young assistant.

We have here a very charming and likable science fiction comedy from France, which doesn't utilize much in the way of special effects, but is well-written and well-acted by the talented cast.  Turning other shrinking movies on their head, the intent is not to explore a new giant world, but instead Marais uses the formula to shrink the beautiful Laurent and carry her in his pocket to rendezvouses for trysts, while detectives are following him at the request of his jealous and possessive fiancee.  This leads to a number of natural comic situations, and although I wouldn't say the film is uproariously funny, there's still chuckles to be had.  Marais may be best known for playing the Beast in Jean Cocteau's 1946 adaptation of Beauty And The Beast, and Fantomas in a series of films, and gives a good performance, but in my opinion Laurent is the star of this film, so appealing as the professor's student whose infatuation with the man turns into a believable love affair.