YOU SAID:

I went to the bathroom and saw my cat playing with his toy

INTO JAPANESE

私はバスルームに行き、彼のおもちゃで遊ぶ猫を見た

BACK INTO ENGLISH

I went to the bathroom and saw a cat play with his toys

INTO JAPANESE

私はバスルームに行き、彼のおもちゃで遊ぶ猫を見た

BACK INTO ENGLISH

I went to the bathroom and saw a cat play with his toys