Loonies at Large (1993)

This comedy brings Pierre Richard and Michel Piccoli together onscreen once again. In the story, former professor Henri Toussaint Piccoli has been locked away in a psychiatric ward for some years for trying to strangle his wife when he found her in bed with another man. Now she has a terminal illness, and wants some sort of reconciliation with him. His therapist (Richard) decides to permit him to visit with her, provided he comes along. Except for his wide mood swings and occasional outbursts of lewd muttering, the professor "passes" for sane fairly easily. Not so the psychotic (Dominique Pinon) who stows away in the psychiatrist's car, who constantly calls attention to the other two.