YOU SAID:

the cat in the hat was a mat in a cat

INTO JAPANESE

帽子の中の猫は猫の中のマットでした

BACK INTO ENGLISH

The cat in the hat was Matt in the cat

INTO JAPANESE

帽子の中の猫は猫の中のマットだった

BACK INTO ENGLISH

The cat in the hat was the mat in the cat

INTO JAPANESE

帽子の中の猫は猫の中のマットだった

BACK INTO ENGLISH

The cat in the hat was the mat in the cat