YOU SAID:

they were acting stupid in that episode.

INTO JAPANESE

彼らは、そのエピソードの愚かな行動していた。

BACK INTO ENGLISH

They are stupid in that episode was in action.

INTO JAPANESE

彼らは愚かなそのエピソードはアクションであった。

BACK INTO ENGLISH

They were in that episode a stupid action.

INTO JAPANESE

彼らはそのエピソードの愚かな行動だった。

BACK INTO ENGLISH

They were the stupid actions of that episode.

INTO JAPANESE

彼らは、そのエピソードの愚かな行動だった。

BACK INTO ENGLISH

They were the stupid actions of that episode.