Unlike many Neil Simon efforts, which were written as plays and then adapted into films, Simon wrote this directly for the screen when he realized that a play would have difficulty portraying the many different locations involved.

The bases of the newly-begun World Trade Center towers, risen to 10 or so stories, are visible in the scenic view of Manhattan from the airplane. They are unmistakable because of their rusty red patina, which was still in place when the towers fell 32 years later.

The first airport scene showing the Kellerman's departure was filmed at MacArthur Airport in Islip, Long Island.

Near the end, as they finally arrive in their hotel room, you can see the Helmsley Building, which is one entrance to Grand Central Station, out of the window to the south. Nice touch.

Ron Carey's first film.

Many of the smaller supporting roles were cast with well known comedians such as Anne Meara, Sandy Baron, Ann Prentiss, Paul Dooley, and Anthony Holland.

Jack Lemmon was almost killed in the manhole explosion scene. The blast was much stronger than anticipated, and instead of only lifting the manhole cover a few inches up and away from the hole, it threw it several feet into the air. A few seconds later, it falls hard in the ground, very close to Jack Lemmon's head. The actor was then hit in his left leg when the cover bounced, and although startled and in pain, he stayed in character. That shot was used in the final film.

Writer Neil Simon originally intended this to be a segment of the play of Plaza Suite (1971). It was entitled "Visitor from Toledo" and was intended to open the play on Broadway but was cut during the rehearsal period. Simon once described the one-act to the 'Newark Eveing News' as being "...about a man who came to New York from out of town and lost his luggage. He got there in the middle of a transit strike. It was snowing. So after he had checked into the Plaza [Hotel] he had this monologue. We put 'Plaza Suite' into rehearsal, and after about the fifth day [the director] 'Mike Nichols' said 'We just have too much show here. If we include that monologue, the curtain will be coming down at midnight'".

Second of four appearances by Jack Lemmon in a film written by Neil Simon. The others were The Odd Couple (1968), The Prisoner of Second Avenue (1975), and The Odd Couple II (1998).

The storyline of "The Out of Towners" is not dissimilar to the later play and movie The Prisoner of Second Avenue (1975), the film version of which also starred Jack Lemmon.

First of three films written by Neil Simon and directed by Arthur Hiller. The second was Plaza Suite (1971) whilst the third was The Lonely Guy (1984) which starred Steve Martin who also starred in this movie's remake The Out-of-Towners (1999).

When George and Gwen are about to board the train, they pass an advert for Plaza Suite, which is another play by Neil Simon.

One of approximately a half dozen Neil Simon-written films which have been remade. The movies include Plaza Suite (1971), The Odd Couple (1968), The Goodbye Girl (1977), The Sunshine Boys (1975), The Heartbreak Kid (1972), Barefoot in the Park (1967) and The Out of Towners (1970).

Robert Evans of Paramount originally offered the film to producer William Castle. A very serious attack of kidney stones caused Castle to miss out on the opportunity.

First cinema feature of Paul Dooley.

The film's opening credits declare instead of "A film by" Arthur Hiller; it's "A Neil Simon story".

The film was remade twenty-nine years later. The remake The Out-of-Towners (1999) starred Steve Martin and Goldie Hawn in the parts played by Jack Lemmon and Sandy Dennis.

An armed robber tries to send George & Gwen to the fictional "Hotel Ashmont" on 51st Street between Lexington and Third Avenues. The NYPD's 17th precinct is actually at that location.