Blooper

Although Amos gives Flynn "large bill" currency notes (25% larger than the "small bills" in use since 1929) when paying Roxie's retainer, Velma and Roxie use anachronistic small bills in the prison scenes.

In Velma and Roxie's final dance number, Roxie changes her shoes. In the beginning, Roxie's shoes have only an ankle strap, and halfway through the number they suddenly develop a T-strap.

When Roxie refuses Velma's money for doing her laundry, Velma puts the money down her shirt. The position of the money changes in every shot.

During the final scene, when Velma and Roxie are dancing, there is lipstick on Roxie's teeth, which disappears (far too quickly) between shots.

At the end of the final dance, the position of Roxie's gun switches many times from behind to in front of her roses.

When Billy talks to the doctor after "confirming" Roxy's pregnancy, he tells the doctor to button his fly. Most trousers and undergarments used buttons, but the expression "fly" only exists because of the eventual use of the zipper fly. While the zipper was technically patented in the 1800's, it was not yet used on clothing and really wasn't used on common garments around the world until the 1930's.

At the end of his "tap dance" cross-examination of Velma, Billy declares "The defense rests!" Very dramatic but since Velma is a rebuttal witness the defense has already rested.

Amos is surprised to learn that the "burglar" Roxy killed was Fred Casely, whom he knew well. But if Amos had known Fred that well, he should have recognized the body right away. The scene may have been intended to show how dull and slow-witted Amos was.

Amos didn't know Fred Casely well. He was just their furniture salesman who he may only have met once a few weeks or months previously. It's entirely plausible that he never got a proper look at the body's face and didn't recognise it.

Near the beginning of the song 'Razzle Dazzle', when Roxie and Billy walk up to the reporters' seating area, a reporter on the left can be seen reloading the flash bulb on his camera. When he lifts up the camera to take a photo, the bulb falls out, yet the flash still goes off.

During the song "Cell Block Tango", tape can be seen on Annie's chest above her black outfit.

There are 50 stars on the US flag in the courtroom (should be 48).

In the 1920s, the electric chair had replaced hanging as Illinois' method of execution.

Flynn is heard on Roxie's radio saying "This all took place on Lake Shore Drive?" Lake Shore Drive wasn't built until 1937 and wasn't even called Lake Shore Drive until 1946.

When Velma Kelly "can't buy that kind of publicity," she pulls out a modern $1 dollar bill, which wasn't used in 1929.

At 1:28, Velma and Momma are listening to the trial on a radio. The tubes are visible, glowing white. Real tubes of that era glow with a soft orange light. If they were glowing white, they would last about an hour, if that.

In their final dance, Velma and Roxie are presented by someone who speaks on a microphone next to them. However, when the second part of their act is introduced, the same voice is heard, but the man who was talking on the microphone has turned around looking at the musicians, and the microphone is far away from his mouth.

During the Roxie Hart song, right after she sings "who says murders not an art" Roxie walks past a line of mirrors. Halfway through the shot the camera crew is visible in the refection just to the right of Roxie.

In the courtroom scene when Billy Flynn does his "tap dance" a mike is visible on the top center of the screen (usually dismissed as projection error, but multiple reports suggest otherwise).

When Hunyak (played by Russian actress) asks Billy for help, she says, "Help me, please" speaking Russian (Pomogite mne pozhaluysta) instead of Hungarian.

When Roxie is delivering fresh towels to Mama's bathroom, she listens in on her and Velma's conversation. When she leaves, she takes the clean towels and leaves the dirty ones.

Assistant District Attorney Harrison is referred to a number of times throughout the film. Illinois has never used the term "District Attorney"- rather, it should be "State's Attorney".