YOU SAID:
Raining cats are falling!
INTO JAPANESE
雨が降っている猫!
BACK INTO ENGLISH
A cat raining!
INTO JAPANESE
猫の雨が降った!
BACK INTO ENGLISH
The cat rained!
INTO JAPANESE
猫は雨が降った!
BACK INTO ENGLISH
The cat rained!
That didn't even make that much sense in English.