When Libby McAusland sits down to lunch at the hospital cafeteria there is spilled coffee in the saucer of her cup. When she picks up the cup in the next shot the spilled coffee is gone.
When one of the characters falls to her death from a hotel window on the 20th floor, the group must plan her funeral. One of them asks if there is to be an "open casket." If someone plummeted to their death from that height, the damage to their remains would be severe enough that displaying the corpse would not be a realistic option.
When arguing politics with Norine, Helena says, "The whole class voted for Roosevelt in the college poll," when she means "the whole group." Pauline Kael, who was watching the filming and following the script, wrote that she pointed this mistake out to Sidney Lumet but he never corrected it.
In one shot of the New York City skyline, the Pan Am Building is clearly visible in the background. The film takes place from 1933 to 1939. Construction of the Pan Am building did not begin until 1960 and it was not completed until 1963.
The setting is supposed to be between 1933-40, however some of the ladies' hairstyles reflect the styles of the mid-60s. Libby (Jessica Walter) is the most notorious of the group, her up-do with pigtails at Kay & Harald's party being the most obvious of the styles.