When the sergeant explains the workings of the IBM typewriter to Columbo, he puts a piece of paper in the machine. The paper is not present when the shot focuses on the ball with letter symbols.
While performing the water trick for the second time, Santini take off his cape twice.
The sign outside the magic club where Santini is working states, "The Cabaret of Magic", which is also the name mentioned by the emcee introducing Santini. However, the letter written by club owner Jesse Jerome to the Department of Immigration refers to his club as "The Magic Circle Club".
When Santini is performing a trick at Columbo's table next to the stage, Colombo accidentally knocks the menu off the table and onto the floor. In the next shot, the menu is back on the table.
The napkin on Santini's tray changes shape and position as he is about to commit the murder after walking upstairs.
In the opening sequence, the villain's hands are seen putting bullets into a revolver and then screwing a silencer onto the muzzle. Silencers are useless on a revolver, as they can't stop the sound that comes out from the side of the gun when it is fired.
When Santani is picking the office lock, he uses only one piece of wire, which he can be seen removing from his coat. Picking a lock requires two pieces of wire in the lock - one to manipulate the pins, and the other to hold the pins in position to be able to turn the lock.
When they are taking the crate out of the water and opening it, the man on screen left will turn out to be Santini, but Santini was seen to be covering his victim and walking through the kitchen during this time. This trick is common in magic acts, but the magician takes his place on-stage long before the tank is raised from the water. The way it worked here only could be done by stopping the film, putting Santini on stage, and then starting filming again.
When they pull the chest out of the tank of water after the murder, the chest shows no evidence of being wet. No water is dripping off of the chest.
It is implied that Lt. Columbo and Sgt. Wilson are working the case together by chance, and that they rarely work together. In the real-life LAPD, Wilson would be Columbo's full-time subordinate and would work directly for him on a daily basis; not occasionally and by surprise.
The building in which The Great Santini is performing is the same building (or at least the facade) where Edna Basket Brown's funeral celebration takes place in Swan Song (1974), and the manager tries to sell Columbo a funeral plan.
When Santini is about to do the vase-on-the-table trick for the woman in the hat, the baby's breath portion of the bouquet is visible just behind the table. The woman can be seen holding the vase down while Santini holds the napkin up, and she then places the vase on the table.
The IBM Selectric does not create a "readable" line of text as it types (as shown as Columbo holds it up to the light). The letters appear as a cascading and diagonal pattern on the used ribbon. It can in fact be recreated by painstaking reconstruction, but nonetheless not readily readable as shown.
When Columbo makes his first visit to the cabaret to interview Santini, he finds Santini practicing card tricks on stage to an empty room. Santini wears a gray sports jacket, but the close-up hand shots of the card tricks he does show that they are being done by someone wearing a jacket with a black-and-white checkered pattern.
One of the detectives says the victim was shot in the heart. The victim was lying face down on the carpet. Yet when the body is removed, the carpet within the tape outline of the body has no blood stain on it.
At the beginning of Santini's performance, a drum roll is heard, but the drummer is shown keeping time (striking cymbals, etc.).
Detective Sergeant John J. Wilson is identified by name not only by Columbo but by himself, and both characters mention having worked together earlier. They did work together before in The Greenhouse Jungle (1972), but Detective Wilson's name (played by Bob Dishy) in that episode is Frederic, not John J.