Kris Bowers, the film's composer, was Mahershala Ali's piano double.

Prior to filming, Viggo Mortensen was invited to meet Nick Vallelonga's family over a six-hour dinner. He said, "It almost destroyed me because I hadn't gained the weight yet - I hadn't expanded my stomach... It was almost lethal..." When the family assumed he was declining more helpings was because he didn't like the food, he felt compelled to finish his plate. But every time he finished a plate, they brought another one. "I said goodbye. We did a picture together. I limped to my rental car and I made a big show of 'oh, I'm driving back to Manhattan!' And I drove around the corner, parked the car, leaned my seat back, undid my belt and lay there for an hour, just groaning."

Nick Vallelonga says he spent a lot of the shoot in tears because the actors' portrayals of his parents were so vivid. "Linda Cardellini, I can't even look at all. She just makes me lose it."

The pizza scene is drawn from real life: Nick Vallelonga said Tony Lip used to order a whole, unsliced pizza pie, fold it and eat it. Upon hearing the anecdote, Viggo Mortensen insisted they try to fit it into the movie. Peter Farrelly protested, saying there were enough funny eating scenes, but agreed to try it. When the crew burst out laughing, he agreed to leave the scene in.

The title and subject matter are a reference to "The Negro Motorist Green Book," also known as "The Negro Travelers' Green Book." Published from 1936-1966, the guide helped African-American travelers find lodging, restaurants, and other businesses that would serve them. It eventually covered most of North America, plus Bermuda and the Caribbean.

The film is dedicated to "Larry the Crow," a bird that hung around the shooting location. Viggo Mortensen cared for the animal after it was hit by a car.

The real Tony Lip is best known for playing Carmine Lupertazzi on The Sopranos and has had roles in several Martin Scorsese movies.

Viggo Mortensen revealed that Louis Venere, one of Nick Vallelonga's real-life relatives, caused continuity problems in the family dinner scenes. He kept eating the food after the director had yelled cut, saying, "what props? This is good fish, c'mon!"

In the Vallelonga family scenes, Tony and Dolores' real family members play most of the relatives.

The piano piece with which Doc wows the crowd at the bar is Chopin's Etude Op. 25 No. 11 "Winter Wind". It is considered one of the most difficult pieces to play, earning a 9 (highest) rating on the Henle Levels of Difficulty scale.

Per Viggo Mortensen's suggestion, the movie has no opening credits or title card. This immerses viewers in the action and makes them forget they're watching a film.

According to Nick Vallelonga, the actor in the hot dog eating contest actually ate hot dogs with Tony Lip.

This is the first dramatic film directed by either of the Farrelly Brothers.

The film won the People's Choice Award at TIFF (Toronto International Film Festival) in September 2018, where it premiered.

Despite being filmed in Louisiana, the winter storm scenes were real. Viggo Mortensen convinced Peter Farrelly and the crew to put in some overtime on the hunch that there was snow in the air. To their surprise, it kept falling and accumulated. They put in a lot of overtime, and were able to cancel a later shoot planned to capture snow scenes in Minnesota.

Costume designer Betsy Heimann fitted Viggo Mortensen's clothing quite tightly; implying Tony bought his suits many years and folded pizzas earlier, and his finances were too constrained to buy new ones. She also explained that the fashion at the time was for trousers to be worn up around the waist, not below the belly. She noticed that Viggo incorporated this into his performance, as Tony regularly pulls his pants up when he walks around, and thought, "He's doing that for me!"

Viggo Mortensen's wardrobe contains many red and blue striped shirts, a tribute to his favorite soccer team, San Lorenzo de Almagro.

The only onscreen drink that Tony doesn't take in one gulp is the KFC soda.

Viggo Mortensen really ate the hot dogs in the Gorman's scene. The production crew provided him with a bucket to spit out the chewed bits between takes, but he found that even less appealing than just swallowing the hot dogs. He ended up eating 15.

One of the songs played by the Don Shirley trio during a montage is "Happy Talk" from Rodgers and Hammerstein's "South Pacific", which, like "Green Book", also deals with the issue of racism. It is unclear, however, if the song was intentionally chosen because of this.

In the shared hotel room scene, some graffiti appears on the wall to the right of Tony's head: "CASL de A", clearly written by Viggo Mortensen, whose favorite soccer team is Club Atletico San Lorenzo de Almagro.

Nick Vallelonga pulled a fast one in hiring his real life family members to play the onscreen family members. He let Viggo Mortensen believe Peter Farrelly had cast them, but suggested to Farrelly that Viggo had vouched for them as actors. The two only figured out the truth a month into the press tour.

Peter Farrelly said he tried to play down the laughs, conscious of his background as a comedic filmmaker. According to him, the interplay of Mahershala Ali and Viggo Mortensen elevated the conversations as written in the script. He cited the "Orpheus" dialogue as an example where the actors' reactions really made the scene.

Viggo Mortensen did so much on-camera eating he claims not to have eaten any of the catered food on set, and would retreat to his trailer during lunch to lie down and undo his belt. "I couldn't tell you what the catering was. I heard the catering was great!"

Doc's chess set has no black squares or pieces.

In the scene where Don first gets into the car, there is a poster advertising the November 10, 1962 folk-music Hootenanny. Headlined by Pete Seeger, this was Bob Dylan's first Carnegie Hall appearance.

Mahershala Ali claims that, in their first production dinner to go over the script, Viggo Mortensen excitedly presented a selection of crucifixes and jade rocks to Peter Farrelly. ("Pete, I found a perfect jade rock!") Farrelly used that stone in the movie.

Peter Farrelly says Viggo Mortensen, a perfectionist, insisted on doing the milk-chugging scene three times because he wasn't happy with the way he had been holding the bottle.

The role of Bobby Rydell, opening act of the film, was originally pushed by producers to be played by Drew Taggart, lead singer of the Chainsmokers, but when He was asked to send in an audition of the song he declined. His contract was pulled and auditions were open. Peter Farrelly and Charles Wessler found Actor/Singer, Von Lewis, to fill the part.

The song Tony sings as he arrives back at home is Tu Scendi Dalle Stelle, a traditional Italian Christmas carol.

The film was entirely shot in Louisiana, with the exception of one day in New York. The scene where Tony stops for a bathroom break, and the New York City exterior shots were all shot on the same day.

A local movie Southern movie theater is showing 'Lawrence of Arabia'. Film didn't go into widespread release until February, 1963. It wasn't seen in NY or La until Dec 21, 1962.

This is Peter Farrelly's first drama after years of filming comedies. Mahershala Ali referred to him as "a first-time filmmaker with 25 years of experience".

This was Universal Pictures' second Univisium 2.00:1 release since Jurassic World (2015) and the third Univisium shot film of 2018 after Hereditary (2018) and A Simple Favor (2018)

Professor Longhair's "Go To The Mardi Gras" is included both in the soundtrack (KFC scene) and the end credits, as a nod to New Orleans, where the film's production was based.

The cars the group drives are 1962 Cadillac Sedan DeVilles. The production used three, two for driving and one for static filming. The "hero car" was so loaded down with filming equipment the coil springs collapsed and the roof caved in.

Viggo Mortensen would play Tony Lip's Sopranos episodes in the background while getting ready in the morning, to get into his rhythms of speech and accent.

Asked about his go-to meal to gain weight, Viggo Mortensen said, "It was Italian food. It was a lot of pizza, a lot of pasta. But it was mainly never saying no to a second or a third helping. Never not trying ALL the desserts. And preferably eating the biggest meal - with a full complement of desserts and appetizers - just before lying down to go to sleep."

A theatre marquee in the background of one town shot shows Lawrence of Arabia (1962) playing. Viggo Mortensen starred in Hidalgo (2004) alongside Omar Sharif, one of Lawrence of Arabia's stars.

Based on Estonian media the prototype of Oleg is actually Estonian cellist Jüri Täht.