Revealing mistake: When Roger is in the bathroom at the urinal, he can see Edwina's reflection in the mirror (as she is, supposedly, inhabiting his body). However, when Roger lets out a particularly big exhale, Edwina's bangs blow slightly upwards, showing that the "mirror" effect is achieved by simply having her stand behind a wall right in front of him. (00:29:45)
Continuity mistake: After Roger is hit on the head with the bowl, it mysteriously disappears from the sidewalk.