The plot, three potential fathers vying to prove that they are the father of the main character's daughter, is used many years later in the stage musical Mamma Mia! This movie is also the basis for another Broadway musical, Carmelina. Mamma Mia was made into a successful film in 2008 set in Greece, Mamma Mia! (2008), rather than Italy. Mamma Mia! Here We Go Again (2018) would follow in 2018, with further family adventures.
Mrs. Campbell's red sports car is a Fiat 1500 Cabrio. Gia's car is a Renault Caravelle. Each taxicab is a Fiat 600 Multipla.
Phil Newman's sons are named after stand up comedians of the day: Lenny, Buddy, Brucie (Lenny Bruce, Buddy Hackett).
By 1968, the old production code was in life support and would soon be given a decent burial. This film was just one example of what was to unfold in a few years, once the age category rating system would be introduced (originally G, M, R, X).
At some drive-in movie theaters, this was the second half of an odd double-bill beginning with Le pont de Remagen (1969).