Continuity mistake: When Tom is tip-toeing past the gate at the start of the cartoon, Spike is sleeping and you can see there is nothing around his neck, but in the next shot a dog collar has suddenly appeared.
Continuity mistake: When Spike grabs hold of Tom's leg, you can see behind him is Tom's tackle box. But when we see the dog in the next shot, the tackle box is nowhere to be seen.
Continuity mistake: When Jerry is sleeping in Tom's tackle box, he takes off his dressing gown and leaves it there when Tom takes him out of the box. But when Jerry races back to the tackle box and starts shivering, the dressing gown has gone.