Goofs

In the beginning, after rat No. 7 is removed from the water, his fur changes from soaked in water to completely dry, to wet, to dry, each time the shot changes.

At about the midway point, Al admonishes Brian for getting lost on the way to the restaurant, making fun of him for not being able to follow a perfect grid and find 62nd St. & 3rd Ave. But in the scene immediately preceding, when Happy invites him to the dinner, she only tells him the name of the restaurant, the street number, time, and that the restaurant is 'kind of Frenchy.' so it's a wonder he was able to find it at all.

At 1:05:01, vomit is not originating from Happy's mouth.

When Al is shopping for a bed, he is quoted a price of $14,000, presumably for the one he tried, with his assistant Gary next to him, so it would be a full size mattress at a minimum (54 inches, or 4 ft 6 inches wide). The size is further implied when Happy later goes to pay for the bed and tries it out for herself, spreading her hands on her sides and still having at least two feet to the edge (the space occupied by the skeleton), making it at least a Queen (60 inches, or 5 feet). However, when Brian delivers it, it is obviously a twin size. You can tell because when they first take it out of the truck and rest it on the sidewalk, the edge of the mattress aligns with Brian's waist.