While there is no electricity during a blackout, the door buzzer seems to work fine.
In the long shot it seems as if the "money sandwich" has potato chips around it. In the close up it doesn't.
It is very out of character that Felix hasn't cleaned up the food by the time that Oscar stages the reenactment of the "crime".
Oscar wonders what a detective like Perry Mason or Charlie Chan would do. Perry Mason was not a detective, but a defense attorney.