The cartoon begins with a demonstration for the Tom and Jerry Cartoon Kit, with which "anyone can now enter the lucrative field of animated cartoons." The items in the kit include the following:
- Tom (described as "one mean, stupid cat")
- Jerry (described as "one sweet, lovable mouse")
- A hammer, knife, and stick of dynamite (collectively referred to as "assorted deadly weapons")
- Coffee and cigarettes (removed from kit and described as being "for the cartoonists")
- A slice of watermelon
The narrator points out, "The result may not make sense, but it will last long enough for you to be comfortably seated before the feature begins." This statement refers to the original theatrical exhibition of the cartoon, in which it ran ahead of a feature film.
At first, the kit is set up by having Jerry eat the watermelon. He spits the seeds out, hitting and waking Tom, who initially grabs the hammer to hit Jerry but instead flicks him in the back of the head. This causes Jerry to swallow his mouthful of seeds, whereupon he starts dancing and shaking his body to make maraca sounds. Tom catches him in a metal can and uses him as a shaker for his own dance; when the effect suddenly stops, Tom peeks in and gets a mouthful of seeds spat into his face. He devours the rest of the watermelon and turns his head into a cannon to fire blasts of seeds at Jerry, who takes cover in the kit box just before Tom hits it, destroying the stick of dynamite.
Jerry winds up lying beneath a book called Judo for Mice, studies it, and emerges with enough fighting skill to easily overpower Tom. Even a stint of training at a boxing gym and use of the knife do not give Tom any advantage against Jerry. Finally, Tom goes to a judo school in order to face him again. The two have a breaking contest, with each trying to outdo the other. The contest ends abruptly when Tom tries to break a huge block of marble, which crashes through the floor and takes him with it.
The unconscious Tom ends up in the battered box. Jerry replaces the lid as the narrator explains, "Our next film will be for the kiddies, and will demonstrate a new poison gas. Thank you and good night." Jerry shuts the box with Tom in the end scene. The music winds to a stop as if it was being played on a slowing phonograph record and Jerry bows to the audience in typical Japanese fashion.
- Main article: The Tom and Jerry Cartoon Kit/Gallery
- As this short reused the Tom thinking footage from Landing Stripling, the knot in his tail exists despite the fact his tail was not tied up at any point in this short.