Continuity: When Gwendolyn holds a match to light Cecily's cigarette, the cigarette is lit already. Also, Gwendolyn's match flame does not come close enough to the end of Cecily's cigarette to light it.
Anachronisms: Jack's plaid tie was trademarked by Burberry in 1924.
Continuity: During Cecily and Gwendolyn's outdoor tea, Cecily cuts a large slice of cake that is served to Gwendolyn and placed on the corner of the tea table. In subsequent shots with both Cecily and Gwendolyn and later, when Jack and Algernon take the ladies' seats at the tea table, the cake and its plate are missing.
Factual errors: In the scene where Algy comes upon his servants playing music together, the banjo shown is a modern "bluegrass style" banjo with 5 strings and a resonator. At the time this movie was set, the banjo was a popular instrument, but it would have been the 4 string, open backed type.
Audio/visual unsynchronized: When Algy is playing the piano for the 'Lady come down' song his hands are moving but the keys of the piano don't move.
Continuity: When Miss Prism opens Dr. Chasuble's portfolio, the second drawing from the top is partially folded, but when she examines it in the next shot, the drawing is neat and unbent in the stack.
Revealing mistakes: When Gwendolen goes to light Cecily's cigarette upon their first meeting, the flame entirely misses the cigarette because of the breeze blowing it away. No matter, it is already lit and Cecily takes a puff from it and exhales smoke.
Continuity: During the song "Lady Come Down" Jack leans against a pillar at the foot of the stairs with one leg crossed in front of the other. The leg that is in front changes from left to right, and back to left again as the camera angle changes.