Continuity mistake: In the scene after Bailey becomes nonexistent and they go to the bar, Clarence and Bailey are thrown out, but when they land they have switched positions. (01:50:20)
Continuity mistake: The old man's cigar disappears when he sends young George to deliver a prescription.
Continuity mistake: The bouncer in Nick's bar has his right hand grasping old man Gower's right shoulder, but the next shot when the bouncer throws Gower out of the bar, the bouncer's left hand is now holding Gower's right shoulder.
Other mistake: During Harry's party, when George is outside talking to his mother she encourages him to see Mary and George says "Point me in the right direction." He then exits right and immediately returns. As he passes by, there is a glitch in the film and for a brief moment everything speeds up. This is most evident if you watch the people dancing in the house because they appear as though they clicked into "fast-forward motion" briefly and then return to normal.
Continuity mistake: In the scene where Old Man Potter is offering George a job, nearly all of the items on Potter's desk - skull, lighter, eye glasses, small ink blotter and magnifying glass - change position as POV shots change from Potter to George. In some cases items disappear completely then reappear, ie. eyeglasses, ink pot and two pens, the liquor case and bells on the corner of the desk, and the pencils beside Potter go from none to one to two, and then none again. (01:07:30 - 01:12:40)
Continuity mistake: The pen in Potter's right hand is instantly placed on his desk as the scene cuts from him to George Bailey when Bailey is begging for Potter's help in replacing the missing $8,000.
Continuity mistake: Outside of Ma Bailey's Boarding House, Clarence is leaning on a mail box, holding his copy of Tom Sawyer. The position of the book changes in Clarence's hands as the shots quick cut from him to George Bailey and back.
Revealing mistake: Near the beginning of the film, young George already has blood coming out of his ears prior to them being slapped by Mr. Gower.
Continuity mistake: Just after George's brother comes home, George is walking across the street and a man is approaching him, but it's then a woman that passes him, not the man.
Continuity mistake: When Ernie is about to take George during his "never born" sequence, if you look at the building next to the taxi, there is the Indian Club. As Ernie is driving along around 20-30 seconds pass inside the cab. When we see outside the cab and Ernie signals to the policeman, you can see the cab has only traveled roughly 20 meters from the Indian Club.
Continuity mistake: While George is in Potter's office begging for $8,000, the snow flakes hanging around on the shoulders of George's coat should have melted away immediately after he enters Potter's office.
Continuity mistake: When George is in the Bridge Tender's office, he says he wishes he had never been born while holding a coffee cup close to his mouth, but the next quick cut of him shows his arms in his lap with no coffee cup.
Continuity mistake: Potter's rent collector is showing Potter a map of the new houses George Bailey built, but a page is folded over on the desk, covering half of an ink pen set on the desk. When the rent collector prepares to leave, that page is now a few inches to the right of the ink pen set (viewer's perspective) and hanging off Potter's desk entirely.
Factual error: When Clarence picks up his copy of "Tom Sawyer" to see if it is dry, the book is in perfect condition, despite their clothes being soaked. The pages of book that had been soaked in water would been swollen and wrinkled, and many pages would very likely have stuck together as the book dried.
Visible crew/equipment: When Sam and his wife get into the car (heading to Florida) George and Mary watch as they drive away, and just as the couple turn around the actor's chalk T-mark is visible on the ground near George's feet. (01:07:10)
Continuity mistake: Ernie hangs out of the window of his cab as Violet Bick strolls by, then ducks into his cab after the car horn blast. A quick shot later and Ernie is again hanging out of the cab's window, watching Violet walk.
Audio problem: When George is talking to Harry on the phone regarding being decorated with a medal of honor, he is at his office. The guy to the right of him starts to say "what is he saying?" but the audio cuts off just before he finishes "saying." The scene cuts to a closer shot of George talking, so why did the audio cut off?
Revealing mistake: When George comes home flustered, his kids are hanging on him. Right after Mary closes the door keeping the littlest boy out, she walks into the kitchen. Watch this scene carefully as the camera tracks backwards. A bad jump cut is obvious.
Continuity mistake: In the scene where Violet and George talk about going up to Mount Bedford, they start their walk down the promenade, close to the intersection where Gowers Drugs and The Bijou theater are visible in the background, along with a tree with no visible branches and a Caucasian couple seated on a park bench facing screen right. At the cut to the closeup, they have moved about 50 to 75 feet further down the promenade, the drug store and theater are no longer visible, the tree behind them now has a branch, the couple is now African American and the park bench is facing screen left. (00:41:30)
Audio problem: The cab driver says "in" twice as he's saying hop in. The scene cuts to a closer angle while he's talking. He says "hop in (cut) in."
Answer: It was a common phrase at the time, like someone saying "oh boy!" or "hot damn."