Revealing mistake: When Julian uses a credit card to open the sliding glass door at his parents' home it's obvious that there is no latch or lock where he inserted the card when the door opens.
Factual error: One of Angel's lyrics (in "Today For You, Tomorrow For Me) refers to the movie "Thelma and Louise." Rent (the movie) is set in 1989-90. "Thelma and Louise" was released in 1991. This was caused when they did the move from Broadway to the screen. The stage show did not specify the year. So when they adapted the stage show to the movie, they didn't check the references. Plus it just sounds cool. (00:28:25)
Visible crew/equipment: Towards the the end, when Scrooge wakes up in his bedroom on Christmas day and is elated to know he is still alive, he goes over and looks in the mirror twice. Both times you can see someone in the mirror reflection in the background, possibly holding a script.
Continuity mistake: When George goes to propose to Melody he brings in three boxes. Then as he is leaving he is carrying all three and then as the camera angle changes the top box disappears.
Continuity mistake: Belle and the Beast are ice skating, but when Belle falls onto the snow, her ice skates have turned to brown boots. (00:08:50)
Factual error: Jack Lemmon cooks spaghetti for Xmas dinner. On New Years Eve he picks up the tennis racket, through which he had poured the spaghetti, and one piece hangs limp from the racket. It would of course, have long dried and be hard as before cooking.
Continuity mistake: In the scene when John Ritter is trying to fire Santa and the elf, there is a cup with candy canes on the edge of his desk. The number of candy canes change with each shot. (00:32:20 - 00:34:10)
Revealing mistake: Towards the end when Harmony calls Perry's phone as she's lying on the ground, Harry grabs the phone and looks at the caller ID to see her name. Unfortunately that's not the display showing who's calling. Anyone who has a Nokia phone will recognise that that's showing the contact list with just two entries - Harmony and a random number. The fact that it says "contacts" at the top of the screen is a bit of a giveaway.
Continuity mistake: In the last shot of Day-Day in bed with two girls, his hat falls off, then is back on, between shots.
Continuity mistake: When Samantha is sitting at the foot of the bed with an ice pack on her head, eating toothpaste, in one shot she spits some toothpaste out and it goes over Chris' hand. In the next shot his hand is clean. (00:36:55)
Revealing mistake: The wires holding up Jacob Marley's floating lock box and chains are visible. (00:32:10)
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: The strings of lights for the reindeer reins change continuously from one strand to two.
Continuity mistake: When Scrooge walks into the Cratchit home at the end, there is a "Home Sweet Home" plaque on the wall. The shot then cuts away from it. The next time the plaque is visible, its lettering has changed.
Continuity mistake: When two Pegasus ponies carry the "Here Comes Christmas" candy cane along the line of ponies, it passes Rainbow Dash four times.
Continuity mistake: Near the end, Mike is hanging the glass angel he got from Artie on the tree. Nina comes in through the front door, leaving the door chain hanging (unlatched), yet, in the very next shot the chain is on.
Continuity mistake: When the guy and girl are sitting in the car, they put the newspaper with duct tape up on the window but later on both the duct tape and newspaper are gone.
Continuity mistake: When the reindeer gets into the house and runs around, it knocks over a TV set. All of the magazines that are on top of the set come crashing to the ground, including a TV Guide with "Get Ready For A Fabulous February" (or something like that) in big letters on the cover. Interesting since the movie is set around Christmas time.
Other mistake: When James Gandolfini hits Ben Affleck over the head with the shovel for burning something in his front yard, he falls, but his head never hits the ground. You can actually see Ben Affleck holding his head up a few inches off the ground. An impossible feat for someone who is supposed to be unconscious.
Other mistake: After Molly crashes the taxi, she is standing outside in the bitter cold. Yet you never see her breath (vapor) when she is speaking or when she is huffing and puffing when confronted by the wolf.