Darby and Joan; old couple living in harmony
A set phrase referring to an elderly couple who live together in affectionate harmony, like the legendary couple from the Noh play 'Takasago'. Often used to describe a happily married old pair.
That old couple is just like Darby and Joan.
Refers to the Noh play 'Takasago' or the location; 高砂の尉と姥 specifically refers to the elderly couple from that play as a symbol of marital harmony.
The pine tree of Takasago, another symbol of longevity and happy marriage, often paired with the couple.
From the Noh play 'Takasago', where an old man (尉) and old woman (姥) appear as spirits of a pine tree, symbolizing a long and harmonious marriage.