You fool = Baka, (A group of fools = bakas?)
 

To answer to the forums rules, yes I read them. this seemed like a very simple question to me at first, but still...

I checked around and have had minimal luck with google and wiki and other places... and translators... then found a thread post here about it... but was in Japanese characters.

So,

I watch anime... easily picked up that Baka means fool\idiot\etc.

However, can't find out the answer to one question:

If some1 walks in a room, and wished to call everyone in the room a fool @ once... "you FOOLS!" or "BAKAS"

Do they say Bakas (as in plural)? Would that be how it is said verbally, i guess is a better question?

The plural in Japanese is not adding an "s" as it is in English. In most cases the singular and the plural are the same word, so in this case the answer would be "BAKA" to a room full of people.

I thought this was going to be a question about how to pluralize the weeabooenglish "baka." I was all set to unload my favorite pseudo-Latin pluralization: "bakae" :)

If you want to call a group of people baka you can pluralize the group.. so you could take おまえ (you) add ら (a pluralizer) and say おまえらはばかだ（お前らは馬鹿だ）。

Anyhow if you want to learn Japanese put down that anime and pick up a real textbook.
You are in no position to be learning your Japanese through anime. It is a horrible source for beginners to start out with, unless you are watching chibi maruko or something.. but somehow i doubt that.

single-plural
fool-fools
馬鹿－馬鹿等（ばから）
馬鹿者－馬鹿者ども
馬鹿者－馬鹿者達

The Japanese suffixes which are equivalent to pleural-indicating "s" or "es" in English would be "ら”, "ども", or "たち（達）".

Hope this helps.

You guys realize the OP does not read Japanese, right?

for what the OP wants to know though I think it is more appropriate to pluralize the group. how exactly would you say "you guys are stupid！" with 馬鹿者達？

anyhow those endings are not equal to the English "es" or "s" considering they would make no sense for other nouns like apples or computers or something.

why not just use みんなはばかです!

because that means "everyone is stupid!" vs, being specific and rude/mean to a group that you want to point out.

add a place and then you get "everyone here/there is stupid" so...the same thing.