The Fantasticks is a musical comedy from 1960. It's about two neighboring fathers who trick their children into falling in love by pretending to feud.
The show's original off-Broadway production ran a total of 42 years (until 2002) and 17,162 performances, making it the world's longest-running musical.
It's typically staged with a very sparse set consisting of a table and ladders to represent the neighboring bedrooms.