The Cat and the Mermouse is a 1949 animated short that is the 43rd Tom and Jerry cartoon. It is one of the better films of the time.
This short is not that original in its setting at first, but eventually is as it goes underwater and of course ends with a twist. That is why it is even better than excellent ‘Cat Fishin’ with which it shares a similar setting. The only problems here are that Jerry is at first forgettable and the beginning is slow plus some action is typical. But everything else is remarkable with Tom being absolutely superb with his hilarious yelps.
The underwater scenes are so intriguing and very well executed with some of the action being very inventive. The sea animals are well utilized and the humor is great. But it succeeds mostly on the strength of the relationship between the two which is superb here and giving us the rare glimpse of their good behavior. The ending is so unexpected, but also so sweet with Jerry trying to reanimate Tom being just so heartwarming and wonderful to behold.