In 1969, Frank gives Claire a set of Ginsu knives as a gift. Ginsu knives were first sold in 1978 under a different name, and the "Ginsu" name was coined in 1983. In addition, the DVD subtitles misspell it "Gensu."
After the encounter with the Ghost of Christmas Past, Frank decides to visit Claire at work. The business card she gave him says "Operation Reach Out" but the doors Frank walks into say "Operation Outreach".
After Frank Cross stumbles on to the stage after breaking out of the sewer, he wrestles with an actor from the fake movie set. He grabs the actor's walking stick and in between shots the stick moves from his right hand to his left.
When Claire hits Frank with the door, she has a roll of wrapping paper in her shopping bag. When she drops her bag to see if he's alright, the paper's gone. When he picks her bag up, the roll is back in the bag.
When Cross gets locked in the back of the cab, he tries to open each door, but the handles come off in his hands. Between taking them off and holding them up by his face, the heavy end of each handle switches to the opposite end.
When Grace is taking Calvin home, she can be seen exiting the 45th Rd-Courthouse Sq station in Queens. But when the Ghost of Christmas Present takes Frank to see Grace and her family, she says she's taking him to Harlem, which is in Manhattan.
The address on Claire's business card reads 514 West 43rd St. But when Frank gets there, he passes a street sign that says 3rd St./900 East. Even if 3rd St. was meant to be the cross street, West 43rd St. would not cross East 3rd St. nor would it be on the 900 East block.
After Frank Cross wakes up in his office after Lew visits him, he drinks some vodka that has a golf ball in it. When he drops the golf ball on his desk, it bounces three times in front of Frank's face. On the second and third bounces, the ball actually goes higher than on its first bounce. Although this is "impossible," it is meant to emphasize the supernatural origins of the ball. Also note that the sound effects correspond with this "supernatural" activity.
When the phone auto-dials (right after the appearance of Lew Hayward) you can see Claire's full name on the phone display. Caller ID wasn't available until 1988 - the year Scrooged was released. It seems a bit strange that Frank has saved the name and number of a woman he hasn't talked to in 15 years on his telephone. When the phone was installed, Frank may have had his secretary or the IT department put everyone in his address book into the phone, and Claire's name probably would have been in there.
During the broadcast of A Christmas Carol, Scrooge tosses a coin to a boy so he can buy a Christmas goose. The shot seen in the control room monitor shows the coin falling in slow motion. This was more than likely a pre-recorded shot used for dramatic emphasis within the broadcast, which is common practice during live telecasts.
During the "Father Loves Beaver" promo, the cookies that are taken out of the oven are already made and upside down. They can be seen to rock from side to side. This is probably a gag about a low budget show's production values.
Frank's second visit with the Ghost of Christmas Past is in 1968 and he is working for IBC. He meets Claire at this time as well. He was four years old in 1955 which makes him only 17, way too young for such a job.
When Frank Cross' office door is being beaten down by Lew Hayward, it is obviously made of metal, as it retains the dents from the impacts on the outside. However, when the door finally shatters, it is clearly made of wood.
Upon entering the office Christmas party in 1968, the Ghost and Frank walk into the room. Despite being invisible to the guests, a woman in a brown dress clearly looks right at them as they move toward her.
The promo for the Christmas Special shown at the beginning of the film contains events that haven't happened yet (sets shown that aren't built yet, etc). For example, the shot of Mary Lou Retton rehearsing her tumbling routine and saying "God bless us, every one" is repeated exactly later in the film.
When Frank enters the sewers you can clearly see that the some of the pieces of ice hanging down are nothing more than pieces of cloth. Watch as they blow in the wind while Frank moves around the sewer area.
Grace, Frank's personal assistant, is portrayed as being poor, but being the PA to the President of the network, Grace should be on a good salary. Even if Frank is not paying her well, she could have got another, better paying job, given the seniority of her current role.
After the Ghost of Christmas Past asks if he can smoke, he takes a puff of a cigar and it is supposed to look like smoke comes out of his ears. However among closer examination you can see that smoke comes out of a tube attached to his upper ear and not the actual ear itself.
When Frank has a meeting with Preston and meets Bryce for the first time, Frank and Preston both order a high ball. When it arrives Preston takes a drink of his and it's a whiskey color, but Frank's is clear with the eyeball in it, showing it's a different kind of drink.