YOU SAID:
The pig that John found looked ahppy
INTO JAPANESE
ジョンが見つけたブタは幸せそうに見えた
BACK INTO ENGLISH
The pig found by John looked happy
INTO JAPANESE
ジョンが見つけた豚は幸せそうに見えた
BACK INTO ENGLISH
The pig found by John looked happy
That didn't even make that much sense in English.