Dr. Jekyll and Mr. Mouse

The film starts with Tom delightfully grabbing a bottle of milk and rushing into the living room to pour it in his bowl and drink it. Just as he begins to drink from his bowl, he notices Jerry drinking his milk. Tom attempts to hit Jerry, but ends up hitting himself in the process. Further attempts to prevent Jerry from drinking the milk prove fruitless. Just then, Tom has an ingenious plan.

The next scene shows Tom craftily mixing several chemicals into his milk, such as mothballs, ammonia and a variety of poisonous substances. He mixes the deadly elixir together with a spoon, but the toxic chemicals cause the spoon to melt. A fly lands on the edge of the bowl and takes a little sip, before crying in pain and dropping dead.

Confident that his potion works, Tom carries the bowl and places it outside Jerry's hole, gleefully watching as Jerry drinks from the bowl. Jerry yells in pain and collapses. Just as Tom is checking that Jerry is dead or not, the full effects of the potion take place. Jerry becomes an oversized, muscular, super-strong version of himself, more than able to defend himself against the cat, scaring Tom into running away. Tom tries to squash Jerry with a large phone book, but the super-rodent effortlessly rips the book into shreds. Tom opens up a safe and jumps inside, closing the door behind him. Jerry's powerful strength allows him to punch through the metal safe and pull Tom out of the resulting hole. As he grabs Tom and smacks him against the safe, the potion's effects wear off and Jerry returns to his normal size.

After drinking some more of the potion and getting further revenge on Tom by grabbing him and slamming him by his whiskers, Jerry reverts to his normal self once again. Jerry hurries towards the bowl of milk, but is stopped by Tom. The cat-and-mouse chase resumes, until Jerry traps Tom in the refrigerator. Jerry hurriedly attempts to make more of the concoction himself. However, Tom claws his way out of the refrigerator and before Jerry has a chance to drink it, Tom gulps down the mixture and ends up growing to an enormous size and then shrinking. The tables are turned, and by the cartoon's end, Jerry is chasing Tom with a fly swatter.