Continuity mistake: In the scene where Satine meets the Duke for the first time in the elephant, Christian is hiding behind the table and Satine is trying to distract the Duke. After she does her 'dance', the Duke asks her if she wants some champagne. When she yells, she reaches out with her left hand. When she is shown again, she is reaching out with her right.
Revealing mistake: Throughout the movie, if you listen closely to Ewan when he whispers, you can hear that his accent switches from English to Scottish.
Continuity mistake: Towards the end of the movie when the cast is singing the finale song and the Argentinian comes out he walks down the stairs twice.
Continuity mistake: In the scene where the Duke and Zidler are negotiating their contract, the background decorations change a few times. The DVD commentary mentions that the scene was shot in both Madrid and Sydney and to look for hair changes, but the statue behind the Duke's shoulder is noticably different depending on the shot. One good tip is to watch for the different camera angles showing that the cameras were not in the same place.
Continuity mistake: From the beginning of the Red Room scene, until the end of "The Pitch," Christian's tie changes in a variety of ways he obviously didn't have time or opportunity to fix, considering all that hiding from the Duke. Christian's tie starts out straight, is removed by Satine during the "big boy" tumble, but later shows up again, perfectly tied during the "Your Song" dance on the roof. It disappears again after the dance on the roof ends, but mysteriously shows back up during different scenes in "The Pitch," untied, and flapping around his neck. No times listed, because its a running occurrence, on the DVD, watch closely from scenes 8-12.
Deliberate mistake: When Satine and Christian are singing "The Elephant Love Medley" and Satine dismisses Christian singing "I'll drink all the time" and then heads down to the heart window of the Red Room. If you watch the chains attached to the elephant's head just after Satine passes under them and before Christian leaves they move as if being struck by something. The actors actually were on safety wires and Satine's hit the chains when she went in. They later edited out the wires so now the chains look as if they were hit by an invisible object.
Continuity mistake: In the Can-Can dance scene, there is a brief shot of Nini Legs-In-The-Air sitting down and spreading her legs as wide apart as they will go. She is dressed entirely in black. The shot changes immediately to the Can-Can dancers all lined up, with Nini standing in the middle wearing a yellow dress. She continues to wear this outfit for the rest of the scene.
Continuity mistake: When they are singing, "And they call them the diamond dogs." the black guy's hat is on, then off, and changed each time you see him in those few moments.