Continuity mistake: In the meeting when they show the advertisement for IBC's Scrooge, the Mary Lou Retton scene used in the commercial is the exact same shot that takes place before the live production of Scrooge days later. It shows Alfre Woodard and her son watching Mary Lou as she flips, which cannot be possible because it took place in the future. (00:04:00 - 01:12:00)
Factual error: The address on Claire's business card reads 514 West 43rd St. When Frank gets there, the street sign is for 3rd St./900 East block. The sign on the building reads "9th Street Temporary Shelter". Along with these discrepancies, taking into consideration that 3rd St. may be the cross street, WEST 43rd would not cross 3rd St. EAST, as they are on opposites sides of Manhattan. Even if the '4' on the sign for 43rd St. were somehow obliterated, 514 still would not be on the 900 East block. (00:53:10 - 00:54:15)
Continuity mistake: When Frank sees what he thinks is the Ghost of Christmas Future in the elevator, he flips out and accidentally clocks Grace in the jaw. She puts her right hand to her face, but in the next shot she's holding her left hand up.
Continuity mistake: After Claire hits Frank in the head with the door, she kneels down to help him up, and she has no purse. In the next shot she has a brown purse in plain sight on her left shoulder.
Continuity mistake: Near the end of the film before Frank starts singing, watch the guy to his left (screen right) in the plaid shirt. He goes from being next to him to behind him and jumps around a few times in the scene.
Continuity mistake: On Claire's business card it says she works at Operation Reach Out, but the sign on the building says Operation Outreach.
Continuity mistake: When Elliot shoots at Frank, he hits a wreath hanging on the wall, and it bursts into flames and falls to the floor. Later when it's laying on the floor however, it has what looks like ashes on the floor around it, but the wreath itself is still perfectly green and not burned at all.
Continuity mistake: In the scene where Bill's old boss comes back to see him notice when Bill shoots him and takes the drink. All of the drink comes out of his chest because of the bullet holes. Well notice his shirt is all wet, then in the next scene when he takes off his hat his chest is all dry.
Continuity mistake: After the Ghost of Christmas Present slaps Frank, his tie gets flipped up over his shoulder. It then alternates being over his shoulder and down on his chest in successive shots.
Continuity mistake: At the end, Frank sees one of the dancers standing under the mistletoe. It cuts to a closeup of the mistletoe which is hanging still. But when it cuts back to the wide shot, the dancer's big hat is hitting the mistletoe, and it's moving around.
Factual error: The Ghost of Christmas Past takes Frank to the year 1969, where he watches his younger self giving Claire a set of twelve Ginsu knives on Christmas Eve. Young Frank even remarks that the Ginsu knives are sharp enough to cut through a tin can as easily as a tomato. Problem is, Ginsu knives didn't arrive on the market until 1978, which is when the tin-can-cutting demonstration was first used.
Visible crew/equipment: When the Ghost of Christmas Present settles to the ground after floating down the stairs at Frank's brother's house, you get a brief glimpse of the wires attached to her back.
Revealing mistake: Near the end, when Eliot enters Frank's office with his rifle, he accidentally shoots into the ceiling. He shoots it at a slight angle, but the rubble falls right on top of his head instead.
Continuity mistake: When the cab is about to crash against the two guys unloading parcels, the guys stare in awe and throw the parcels up in the air. Shot cuts to the cab skidding and the guys are back to calmly unloading parcels and repeating the previous movements.
Continuity mistake: When Frank steps in the cab the doorman disappears in the immediate angle from the inside.
Visible crew/equipment: A stage light is reflected on Lou-Old boss' sunglasses.
Character mistake: When Frank opens the present in his office and finds the picture frame from his brother inside, he reads what is supposedly written on the frame out loud: "To Frank, the best brother a guy ever had. Merry Christmas." However, instead of Merry Christmas, it says Love, James.
Continuity mistake: The Ghost of Christmas Present introduces herself to Frank Cross by grabbing his tie while floating. When she comes down to earth, she's not holding it.
Deliberate mistake: In the end scene at the TV set, Scrooge tosses a coin out the window, and the camera follows the coin as it falls in slow motion. The people in the control room also watch this on their monitors. Problem is, this is a live broadcast and filming/watching something live in slow motion is impossible.
Other mistake: When Frank and the Ghost of Christmas Past are at the office Party where the younger Frank is still working, as they stand by the entrance door two women leaving move in closer to try and avoid bumping them - despite the fact that the Ghost said earlier they couldn't be seen or affect what's going on.
Answer: It's a vision, not reality, so one could interpret it either way. I think it's more powerful if Calvin is seeing Frank, silently accusing him of being (at least partially) responsible for his (Calvin's) situation.