During Hyde's first visit to the Variety Music Hall, he reaches over the railing to trip a waiter with his cane. As he lurches around to grab his cane, he knocks his top hat off the railing and it lands on the floor next to the waiter. In the next shot, Hyde is holding onto the hat as he lashes out with his cane.
When Mr. Hyde and Ivy sit down in front each other in the Variety Music Hall, the objects on the wall behind them change repeatedly between shots.
When Hyde first meets Ivy, he tells her he knows she lives in some pig sty on Baptin's Court. But later, a news item about Ivy identifies her address as Diadem Court. (The closed-captioning in the first scene actually reads "Diadem Court" despite what Hyde is heard saying.)
When Dr. Jekyll leaves for his walk in the park, it can be seen that it is dark outside his house. When he is walking through the park, it appears to be daytime. At the party implied to take place around the same time, they complain about Jekyll not being there "tonight."
When Dr. Jekyll is making his first portion of the mixture to transform from Jekyll to Hyde, the glass is very dirty and the glass can't be seen through. When he lifts the glass in front of the mirror, it's perfectly clean.
The credits describe Robert Louis Stevenson's original story as a novel. It is in fact a short story.
When Dr. Jekyll is first seen in the mirror, looking directly into the camera, the effect is achieved by filming Fredric March through a large hole in the wall framed to look like a mirror. On the other side there is a reverse of the set, making it appear as though it is a reflection. Looking carefully, it can be noticed that the crystals hanging from the two candle sticks are not moving in unison.
When Hyde looks into the mirror through the subjective camera, his "reflection" has two stains on his shirt on what would be the right hand side of the shirt if a true mirror image. However, in the next shot where both the mirror image and the real image of Hyde are seen, the stains are now on the left hand side of the shirt. This confirms that the subjective camera view was achieved by the 'mirror' really being a hole in the wall with the actor facing the camera.
When Mr. Hyde is toasting Ivy Pearson at the music hall and is standing in profile, the shape of the skull cap altering the shape of his head can be seen.
After Jekyll turns into Hyde while sitting on the park bench, he repeats the word "death". When he laughs after saying the word "death", two rows of bottom teeth can be seen in his mouth. The bottom row of March's actual teeth are visible along with the fake set in front of them.
In the opening scene, as Jekyll looks into the mirror through the subjective camera, his "reflection" turns away from the mirror before the camera, (supposedly Jekyll's viewpoint) does.
After Muriel's father consents for Jekyll & Muriel to be married the next month, Jekyll goes home and plays part of Bach's "Toccata & Fugue in D minor" on the organ. There is a mid-shot with March playing the keyboard, then there is a close-up of the hands on the keyboard. The close-up hands are an obvious double, as they are playing the piece correctly. March's mid-shot has his left hand ascending on the keyboard while the notes of the music playing are descending.
Immediately after Hyde changes to Jekyll in front of Dr. Lanyon, he moves his head and briefly reveals the padded armature attached to the back of his chair, intended to hold his head in the same position while the makeup artists worked on various stages of his transformation.
At the beginning of the movie, when Jekyll is putting on his cape in the "mirror", the reflection of a crewmember can be seen flitting across his stomach in the glass.
Miriam Hopkins's character is listed as Ivy Pierson in the end credits. However in the movie, it is listed as Ivy Pearson in a newspaper article.
Dr Jekyll, when mentioning his fiancee to his servant, refers to her as "Muriel." This would have been considered over-familiar. A gentleman would have referred to his fiancee, when talking to a servant, as "Miss Carew."