Roz hits Frank at the party on the left side of his face, but walking home he's ruefully rubbing the right side of his face.
The revolver that Frank finds in the closet drawer is a Colt .357 magnum. Later he shoots a fish with it. But when Roz eats the fish and feels something hard in her mouth, she spits out a 9mm bullet, which is completely different from any bullets fired from .357 magnums.
As O'Malley walks down the hallway of the house that's been robbed, a member of the camera crew brushes past a potted plant making the branches whip back toward the actors on screen.
Roz and Frank dodge the cops at the Narragansett train station, but no train goes through Narragansett, RI.