Lorelei has slender hands with long fingers and her nails are manicured. But when she pulls the roll of film out of Ernie's pants with her right hand, the hand is short with thick fingers and her nails are cut and unpolished.
Lorelei's hair before and just after she performs "Diamonds are a Girl's Best Friend" is different to the style that she wears during her performance.
When the ship is shown docking, the tops of the funnels have a wide red band but, seconds later, when the whistle is shown blowing, they are entirely black.
The "Two Little Girls From Little Rock" number ends with Dorothy near stage right and Lorelei near stage left. As the girls leave the stage, Dorothy is near stage left and Lorelei is near stage right.
In the later part of the movie when the girls are talking, Lorelei has on bright red lipstick which turns faint pink a few seconds later.
In the "Ain't There Anyone Here for Love" number, just before Dorothy falls into the pool (which was unplanned), it is clear that one of the divers slips before his takeoff, and his legs smash rather heavily into her head.
When Lorelei is seeing Gus off at the ship, she says "Bye, lover!", but her lips do not move.
It takes over 3 hours to get from Cherbourg (where the boat docks) to Paris, yet the montage indicates that the girls merely got off the boat and spent the day in Paris without having to travel.
Lady Beekman tells Lorelei that she always carries her tiara with her as she is afraid to leave it in the stateroom, yet Piggy is somehow able to get hold of the tiara without his wife's knowledge.
During the "Ain't There Anyone Here for Love?" number, when Dorothy is walking between the two lines of athletes doing knee-bends, one of the men on the left towards the back gets up too late and fails to do his bend in time with the others.
During her confrontation with Lady Beekman at the hotel, Lorelei calls Piggy "Lord Beekman". Later in the courtroom, the Magistrate calls Piggy "Lord Beekman", and Pritchard addresses Piggy as "Your Lordship". Piggy holds a knighthood, not a peerage, and would never be addressed as anything other than "Sir Francis".
Henry Spofford III's guardians allow him to attend the dinner then walk the ship's deck unchaperoned.
Dorothy asks Ernie to get her a pack of cigarettes, yet she doesn't tell him which brand, nor does he ask her.