YOU SAID:

The cat crawled on my underwear.

INTO JAPANESE

猫は私の下着をcいました。

BACK INTO ENGLISH

The cat was in my underwear.

INTO JAPANESE

猫は私の下着でした。

BACK INTO ENGLISH

The cat was my underwear.

INTO JAPANESE

猫は私の下着でした。

BACK INTO ENGLISH

The cat was my underwear.