When the Cat first gets dressed, he puts on tap shoes. However, once he gets to Alex's apartment, he is wearing dress shoes.
When the Cat tries to escape Alex's apartment, he jumps through a window and the sound of glass shattering is heard. However, in the beginning of the film, which takes place the day after the Cat's death, the window is not broken.
When the Cat coughs up blood, some blood can be seen on the brim of his hat before it is shown in his hands.
The fish that is served is actual chicken.
The blood that the Cat coughs up is obviously ketchup.