YOU SAID:
Everbody in the room is an idiot
INTO JAPANESE
部屋で Everbody が、白痴です。
BACK INTO ENGLISH
Everbody is the idiot in the room.
INTO JAPANESE
Everbody が部屋に白痴です。
BACK INTO ENGLISH
Everbody is the idiot in the room.
That didn't even make that much sense in English.