Before singing at Folsom, Johnny is touching the blade of a table saw with a glass of relatively clear water next to it. Later when he holds the glass for the crowd, the water has turned dirty and yellow.
When June goes to the theater one morning on the tour to meet the boys, she finds they've partied all night and she becomes angry. In the shot of her approaching the stage, only 3 bottles are within reach. When she throws them, she throws 4 bottles.
While Johnny and June sing the duet "Jackson" onstage, June's hairdo changes during the scene. In the beginning June's hair is parted down the middle with long bangs tucked behind her ears. When June sashays to the side to allow Johnny a solo moment to sing his part, just a few moments later she sashays back with an elegant upswept hairdo which remains through the end of the song and scene.
At the Texarkana show, John's guitar gets caught on June's dress. When they separate, John has a piece of the dress in his hand. When June is on stage later there is no damage to her dress.
Throughout the entire film, the brown contact lenses Joaquin Phoenix wears come and go.
"I Still Miss Someone" was about June Carter Cash, not Jack. "Walk the Line" was about Johnny Cash's first wife, Vivian.
"Ring of Fire" was written earlier than 1965. Anita Carter released it in early 1963, and Cash released his own version of it later that same year. It is shown as being written after 1965 by the film's chronology.
In 1968, when Vivian left John, all four of their girls had been born. Only three girls are shown crying during their final fight and in the car as Vivian is driving away.
When Johnny Cash is reading letters he received (mostly from inmates), the movie shows one from the Texas State Penitentiary in Austin. The Texas State Penitentiary is in Huntsville, TX.
When in Germany Johnny Cash is shopping for a guitar. In the music store you can see a Fender Telecaster. These guitars were not for sale in Europe in the early 50s. The Telecaster and Precision Bass in the store were obviously used and most likely from G.I.s who needed the cash.
At the tense Thanksgiving dinner with the Cashes and the Carters at Johnny's Tennessee home, the scenery has green leafy trees. In late November, all would be bare except pines & firs.
When Johnny is in the bed eating strawberries with June, he is not wearing his brown contact lenses.
After Johnny leaves June's house after walking from Nashville, it rains later in the scene. Johnny passes out and falls on wet grass and mud. The next morning, when he wakes up near the house he eventually buys, his face and white shirt are clean. They should have been dirty from wet grass, if not muddy.
When Johnny goes to the Carter family's home to visit June, it's supposed to be fall (pumpkins on the porch), but crepe myrtle trees are blooming along the driveway. Those are usually done by August.
When Johnny and June are talking in the motel after his first performance, when June hands him the newspaper showing him that Cry Cry Cry is #14 on the article about the top 15 albums thing, it shows there's two songs at #14 instead of #14 and #15.
Johnny is shown touring with Elvis, Jerry Lee, and June for Sun Records early in the movie. In fact this could not have happened. By the time Jerry Lee Lewis was signed to Sun Records. Elvis Presley was already recording for RCA, and touring on his own.
In one mid-1960s scene, Waylon Jennings has long hair and a beard. At the time, Waylon was clean-shaven, with short, slicked back hair. He adopted the beard and long hair in the mid-1970s "outlaw" era.
When Johnny first looks into Sun Studios, and sees Elvis Presley recording Milk Cow Boogie, Elvis is playing with a guitarist, bass player, and drummer. While with Sun records, Elvis's band consisted of Bill Black on bass and Scotty Moore on lead guitar, with Elvis himself playing rhythm. Drummer D.J. Fontana didn't join them until Elvis signed with RCA Victor and went north.
In an early scene, Johnny and Jack Cash walk down the road on their way to the fishing hole. Johnny quotes a line from a Foghorn Leghorn cartoon. The scene takes place in 1944; the cartoon," All Fowled Up " was released in 1955.
Heavenly Highway Hymns, which Johnny's mother gives him early in the movie, was published in 1956.
Jerry Lee Lewis is backed up by a bass player playing a Fender Precision electric bass, but the bass heard on the soundtrack is an acoustic upright bass.
Before Johnny passes out on stage from overdosing, if you look closely, his mouth never moves when he says "I'm O.K."; he simply waves his hand.
The second time that the band is in the Folsom prison, when Johnny is introduced, the guitar player (playing the telecaster) is playing different chords than what is heard.
When Jerry Lee Lewis plays the piano, you hear the last note after he has walked away from it.
At one point, June asks John where his car is. He answers, "Piss and Makeup." However, the DVD subtitles read "Kiss and make up."
Steadicam and operator are visible during drum solo approx 45 minutes into film.
While June is introducing Johnny for the next number, a reflection of a spotlight can be seen on her stage microphone.
A 1944 scene shows Johnny listening to June Carter on the radio. The announcer says "10-year-old June Carter". She was 14 or 15 in 1944.
When Johnny and June are in the store in Wheeling, WV, the thick southern accents of the locals are not accurate to the region. In reality, the Northern West Virginia accent found in Wheeling is very close to a standard American accent but with a few decidedly east coast tones..
When Johny and June are leaving the store with the fishing poles in Wheeling, WV, June says "I think there's a lake this way". There are no lakes near downtown Wheeling; however, the Ohio River runs along the entire length of the city.
When Johnny is seen playing with his band for the first time on his porch, Marshall Grant's bass is marked with tape as fret markers with the notes written on them. But you can see there's a whole step between "B" and "C". Any musician would know there is only a half step between "B" and "C" and "E" and "F".
When Johnny is going through letters from inmates, he picks up one from Folsom inmate Glen Sherley. The letter is signed "Glen Shirley".