YOU SAID:
once upon a time there was a cat.
INTO JAPANESE
昔々猫がいました。
BACK INTO ENGLISH
Once upon a time there was a cat.
INTO JAPANESE
昔々、猫がいました。
BACK INTO ENGLISH
Once upon a time, there was a cat.
INTO JAPANESE
むかしむかし、猫がいました。
BACK INTO ENGLISH
Once upon a time, there was a cat.
That didn't even make that much sense in English.