During the opening and closing credits, the music is from W.A. Mozart's Serenade # 13 for strings in G Major, K. 525, better known as "Eine Kleine Nachtmusik". In addition, the music during the scene where Michael is helping Granny out of her wet clothes and then again during several subsequent scenes involving Granny is a re-write of a portion of the 1st movement from Beethoven's Piano Concerto # 5, also known as the "Emperor" Concerto. It is uncertain why this went unmentioned in the movie's credits, as if James Newton Howard was the original composer of this music.
This was the first collaboration between Director Michael Hoffman and Composer James Newton Howard. They would go on to work together on Restoration (which featured a similar score to this film) and One Fine Day.
The film was originally titled "Sisters" which was changed by the studio to "Some Girls" to appeal to teens as a sex farce, which the trailers depicted as well as to avoid confusion with Brian DePalma's film from 1973 which had the same title.
Filmed during December 1987 around Christmastime which explains the snowy atmosphere the film captures.
One of the many films during the mid to late 1980s which Patrick Dempsey played a teen or a late teen /adult which included Heaven Help Us, Meatballs 3, Can't Buy Me Love, Loverboy and Happy Together which came out a year later