During a storm, Tom is trying to find a place to stay after being thrown out of a horse-drawn wagon. In the meantime, Jerry is assisting a mad scientist in a castle. They take Cat and strap him to a table next to a dog that is strapped to another table. The mad scientist and Jerry push a number of buttons and controls to switch the brains of the cat and dog, that is, orange cat now has a dog's brain and vice versa. The mad scientist gives the "cat" to Jerry as a companion. While they are sleeping, Tom approaches the castle, noticing Jerry. Cat (with a dog brain) growls and threatens Tom. Tom tries to convince "cat" that he is a cat, but fails. Over the next few minutes, Tom's efforts to catch Jerry are thwarted by "cat". As Tom runs off in fright, he comes into contact with other animals that the mad scientist has experimented on, including a chirping elephant, a chicken that bleats like a lamb, a mooing cuckoo-bird, a dog whose brain was switched with "cat". Tom begs Jerry to help him get out of the castle, to which the mouse roars like the MGM Lion, Leo, and Tom gets out of the castle out of fear and runs away.
- Mad Scientist
- Blue Dog
- Unnamed cats
- Coo Coo bird
On July 18, 1961, MGM announced that it was going to resume filming of Tom and Jerry cartoons.
- This cartoon was originally going to be called "Dogging the Cat".
- This is a cartoon that features animals that had their bodies switch:
- A dog in cat's body.
- A bird in an elephant's body.
- A goat in a chicken's body.
- A cat in a dog's body.
- A cow in a bird's body.
- This is the only MGM cartoon to be written by Eli Bauer, a story man best known for his work on TerryToons.
- According to Gene, Lightning did not have his brain swapped, he just had his animal instincts swapped.
- This film was released in 1961, however the copyright year is written as MCMLX (1960). This is maybe due to its production year.
- The first cartoon to use the new logo for the Gene Deitch-era happy Jerry awhile Tom grins it was used in (except in High Steaks) until Landing Stripling.
- The only cartoon to use a shocked Jerry in the "Tom and Jerry" screen, awhile "The End" screen shows a defeated Tom.
- The blue dog in this short make a close resemblance to Spike, it's unknown if it's him or another dog.
- This was the first T&J cartoon of the 1960s.