YOU SAID:

That boy is so stupid his brain fell out

INTO JAPANESE

その少年はとても愚かで、脳が落ちた

BACK INTO ENGLISH

That boy was so stupid that the brain fell.

INTO JAPANESE

その少年は脳が落ちるほど馬鹿だった。

BACK INTO ENGLISH

The boy was stupid enough to let the brain fall.

INTO JAPANESE

少年は脳が倒れるほど馬鹿だった。

BACK INTO ENGLISH

The boy was stupid enough to let the brain fell.

INTO JAPANESE

少年は脳が落ちるほど馬鹿だった。

BACK INTO ENGLISH

The boy was stupid enough to let the brain fall.

INTO JAPANESE

少年は脳が倒れるほど馬鹿だった。

BACK INTO ENGLISH

The boy was stupid enough to let the brain fell.

INTO JAPANESE

少年は脳が落ちるほど馬鹿だった。