During the scene where the guys are leaning on Nerf to take them for a ride in his mother's car, an extra in a yellow dress can be seen walking to the corner behind them through the car window at an average pace. When they take off a few seconds later, she is seen already having crossed the street, lucky for her but bad for continuity since, in reality, at the pace she was going, she would have been directly in front of the car and hit as the boys took off.
When Antonio attacks Reaper in the convenience store, it is night time. Immediately after this happens, Dito and Mike go to Frank's apartment. The lighting and view outside the windows make it obvious that it is daytime when they are at Frank's, but as soon as they leave, it is nighttime again.
For the first scene in the 1980s, Dito walks home with Antonio and Nerf. When they go into Dito's house - and their clothing implies it's continuous - Giuseppe has suddenly joined them and Nerf is nowhere to be seen.
The song "New York Groove" is incorrectly credited to KISS. While he was a member of KISS at the time, and while KISS performed this song during their tours in the late 70's and early 80's, the song is actually from Ace Frehley's 1978 self titled solo album.
When Dito is flying from California to New York, the airplane seat is an "old' Air New Zealand seat cover. The cover is probably from around the correct time, but Air NZ have never flown to New York.
In the 1980s scenes on the subway, scanning the rooftops, you can see many cellphone towers.
In a scene set in New York City during the early 1980s, a flyer alleging a conspiracy related to the terrorist attacks on the USA of 11 September 2001 is taped to a lamp-post during a dolly shot.
In one shot of the subway, American flags are visible next to the subway windows. These were added after the attacks of 9/11, years after the movie takes place.
After passing Mama's Food Store on the way to see Frank, Dito and Nerf pass a sign saying "Miracle Garden". That style of sign was not put up on New York parks till the 1990's.
In the 1980s scenes the red hand/green walking person can be clearly seen at the street crossing, but in NYC at that time the older walk/don't walk signs were being used.
In the Scene where his brother gets hit by the train, as the train is passing by the cameraman's refection is visible as it passes by.
In the Alley scene where Mike gets shot, a cameraman's shadow is briefly visible on the guy with a white shirt on.
Boom mic shadow in the 26th min on the lower right hand side of the screen, in the scene were the father beats Antionio.