In the opening shot, there is an open door behind Ollie's head. In the next, close-up shot, the door is closed, and in the following shot it is open again.
Ollie is in bed next to the tray of milk bottles, while Stan is asleep in between him and the crying baby. Half asleep and not looking, Ollie "feeds" the milk bottle to Stan, thinking he is giving it to the baby. When the bottle is empty, Ollie gets another from the tray. As he moves it towards Stan, it is obvious the bottle is empty - the stripes on Ollie's pajamas can be seen through it. The camera cuts to include Stan, and now, as the bottle nears Stan's lips, it is full of milk.
When Ollie chases Stan out of the kitchen, he loses a slipper from his right foot and it flies out the door. In the next shot it is back on his foot again.
The neighbour the Boys meet on the landing is clearly seen entering the bathroom further down the corridor but as Ollie enters his apartment the neighbour can be seen outside the bathroom.