When Mr. Jeffries goes to the docks to pick up August, various shots show him with and without iPod headphones in.
One of the signs that the Wizard tears down (we see a close-up of it as he rips it off a pole) says Evan Grady - Missing, not Evan Taylor. This is not long before the police raid the place where the Wizard and all the kids stay.
Robin Williams' character "Wizard", depending on the scene, appears to have two different hair colors. In some scenes, he appears to have red hair and sideburns and in other scenes a brownish auburn color.
When Louis's brother takes the picture of Louis and Lyla on the rooftop couch, Lyla has her hand on Louis's arm across her chest, and he has his other hand on top of hers. Whenever you see the photo for the rest of the movie, however, his hand isn't over hers.
When Arthur is taking August to Wizard's for the first time, August is holding a can of soda in one hand, while Arthur is holding the pizza box. In the next shot, August is holding the pizza box, but no can and there would have been no way he would have disposed of it or taken the box from Arthur.
When August teaches an orchestra member how to perform his music on the rim of a wine glass, he grips the bowl instead of the stem, which would render it impossible to play.
Because of his despair for losing Lyla, Louis does not play his guitar for eleven years. When he decides to start playing again, he takes out his guitar and plucks every string. His guitar is perfectly tuned, and this makes no sense. If you go so long as a month without touching your instrument, it will go severely out of tune. And he didn't tune it off camera before he did this, as we see him open the dusty case for the first time in a decade and play the strings immediately afterward.
Evan (August) goes missing in February of 2006 (according to the missing poster), and mentions to Louis that he has been playing for six months. This isn't clear whether he means only his time at Juilliard, or the time up to and including his time at the school. It is possible to have him missing in February, be on the streets, study at Juilliard, and have the spring concert in Central Park, depending on how long August was on the streets. This is borne out by a scene (while August was in Julliard) of Louis sitting in the park in the snow; August must have entered Juilliard in the fall, and had his concert in the spring.
After 12 years, Lyla and Louis do not look a single day older.
When the hospital is calling to inform Lyla about her father, her phone rings and then you start hearing the message being left with no time for the other person to hear the outgoing message that we hear later in the movie.
When Louis was in New York before August was born. A Verizon Wireless advertisement is shown on one of the buildings. August was born in 1995 while Verizon Wireless was founded in 2000.
The guitar that Louis is playing in the 1994 scenes appears to be a Gibson CS-336F model which was not manufactured by Gibson until 2002.
The license plates on the cars in NYC have the design of the current New York License plates. However, the part of the movie where Louis is chasing Lyla is supposed to take place 11 yrs prior to present day, being 1995-1996. Those license plates were not issued until many years later, probably 1999-2000.
When August was playing the piano at the church for the first time, he played a note, then two more to the left, and got a higher tone when he should have gotten a lower one. He then plays two notes to the right of the original pitch, and gets lower tones. This is exactly reversed from what should have occurred.
As Louis Connelly is walking to his limo, while speaking on his cell phone, his voice clearly does not match up with his mouth movements.
When Evan (August) is at the pipe organ in the church, at one point he is seen from behind. At this time, one hears some high notes descending in a scale-like pattern. To play this, August's right hand would have to be far to the right of the organ keyboard. It is not; it is close to his body, near the middle of the keyboard(s).
When August is playing guitar in the park the first time, there are close-ups to his fingers. But the fingers are those of an adult.
When Evan (August) meets Mr. Jeffries for the first time, Freddie Highmore's microphone pack attached to the back of his pants is visible as he gets up from the table.
During Louis' unsuccessful trip to Chicago to try to locate Lyla, he's briefly questioned by two police officers in a squad car outside her apartment. Chicago police cars have blue roof lights, but this one has a red light bar on top, and appears to be a New York squad car, filmed from a tight angle to obscure its actual markings.
In addition to the already-reported lack of an El train on Second Ave. in front of the site of the former Fillmore East (there once was a 2nd Ave El but it was torn down in the 1940's), the film portrays the Second Avenue facing front of the former Fillmore East as a dilapidated version of its former self, still sporting the old Fillmore East's marquee & still labeled as such. In fact, the Fillmore East's former entrance/lobby area is and for quite some time has been a redeveloped bank branch.
A policeman chases August out of the former Fillmore East and up the stairs of an elevated subway station, but there are no elevated subway stations in lower Manhattan, where the Fillmore East was located.
When Evan/August is in the church, he starts writing down his composition, using the proper symbols for each type of note, even complex ones that only experienced musicians would know, but there is no explanation of how or where he would have learned these notes.
When Arthur leaves the park after meeting Evan, he leaves his amp behind.
When the missing poster is shown, the DOB says Dec. 17, 1995 and the missing date says Feb. 9, 2006, but the age now says 12 yrs.
On the signs for the concert, August's Rhapsody is called "August Rhapsody" even though on the music sheets it's called "August's Rhapsody".