If you go to Gametrailers usermovies section you can videos of each of these levels.

Donkey Kong (Arcade) is the 41st stage.

Yep. Here's a video of it.

http://www.youtube.com/watch?v=sW9AywYprtY

Maxwell, is that a typing mistake? Sure there isn't 50 brawl matches?

Also, an off-topic question, kind of.

Is there off-line co-op in brawl? I have yet to see that...

Yes there is.  

 I have also edited the first post with all our new information. 

 No it's right, Ness is the first character to be unlocked, so I believe so he's the easiest to unlock.

OMG!!! Donkey Kong level!! LOVE IT!!

I've been hoping for that since we learned there were ladders and barrels. I wonder if you ever get the first level where DK is tosses barrels down at you. That'd be great if it appeared every so often instead.

Wow 41 stages is a TON.... That is almost double of Melee I think. And will user create stages you will never get board with the stages. Did they bring any of the only N64 stages back?

^ I don't think so, but looking at the new stages, WHO NEEDS THEM? seriously you can probably make similar ones through the stage editor, they're pretty basic.