First film role of any kind for Jonathan Goldsmith (as Jonathan Lippe), who portrayed Teddy Manson, and who is now much better known as "The Most Interesting Man in the World" from Dos Equis beer TV commercials.
To promote the upcoming release of the film, George Hamilton appeared on a September 1963 episode of I've Got a Secret (1952), a prime time game show in which a panel of celebrities attempted to discover the guest's "secret." Hamilton's secret? The actor identified as Hamilton and grilled by the panel (who failed to guess his secret) was that he was not actually Hamilton at all but instead a dark-haired handsome sort-of-look-alike pretending to be Hamilton. The real Hamilton showed up at the end of the spot and earned the admiration of panellist Henry Morgan who expressed astonishment that any performer of Hamilton's stature was secure enough to take part in a stunt which, in essence, pointed up the fact that he was unrecognisable to a quartet of supposedly in-the-know celebrities.
An actor named Archie Leach is among Hart's group of New York friends in the film. He's obviously Cary Grant--Archie Leach is his real name--but Convy makes no attempt to imitate him or even an English accent.
Although completed in 1963, not released until 1965 as second half of double bill with Dear Heart (1964).
George Hamilton later complained that "Schary de-ethnicized the entire production and took out the brilliance for good measure".