Revealing mistake: When Gypsy tries to hit Helen with her weapon, she misses and hits a table instead, causing one of its leg to break off. However before the weapon even hits the table you can see the leg coming off from the table; obviously being pulled off.
Revealing mistake: When Rolfe is walking down the hallway to Sally's apartment, there is an orb where the hallway is lighter colored and his legs seem to jump and undulate due to the special effect used to hide the fact that the actor is actually full-sized, walking on his knees.