Wakko is the younger brother.  He has blissed-out facial expressions which include something called a "gookie." There really is no way to explain this expression but "what the...."  He is the cartoon charater equivalent of an atomic bomb making him the Daffy Duck of the group.  He is the most destructive character in the history of cartoondom.  Whenever he pushes or pulls results in a chain reaction of unintentional chaos.  His siblings are well aware of Wakko's innate talent, and they employ him in this roll to full effect.
      Unlike his older brother, he has no puns and is no fast talker, just nonstop off the wall literal translations.  He has been smacked on the head with a mallet too many times.  He finds most things amusing.  He is the king of props.  He carries a gag bag out of which he can pull any object we can think of.  He will nod "yes" and say "no." He walks backwards as easy as forwards and means everything he says except what he means.  He loves his siblings to pieces and is very rarely seen without them at his side. He is apt to kiss anyone at anytime for any reason.  He is the looniest of the loony.  And if someone where to hurt his feelings...he would be VERY hurt.
      While Yakko is verbally irreverent, Wakko is physically irreverent.  He is completely off the wall.  He does things in reverse.  He may eat anything at anytime, perhaps for shock value, but most likely because it just might taste good (he reminds me of my dog).
      If you were a bad guy and found Wakko's playful side annoying, pray that you don't see the other side.  'Cause when Wakko gets steamed, you get scalded.  Wakko has a temper that rarely gets unleashed, but when it does, he becomes a tornado of destruction.  When he starts to boil over, Yakko and Dot recognize the simptons, shake their heads and look at the victim to say: "You shouldn't have said that," or "I'd apologize if I were you."
      He's constantly pretending to be one animal or another.  He'll bark like a dog, and give someone a big sloppy lick on the face. 
      Like a nanny goat, Wakko will eat anything, adding salt and pepper to it until it suits his taste.  This grosses out and/or baffles foes.
      Wakko can pull off his tail and use them as props (cranks, ropes, mallets, golf clubs, etc.)
      He is incredibly amused by butts.  He finds them the funniest thing of this century. He often mentions his butt in more than one episode. Yakko and Dot are pretty much not as amused by them as their brother. 
      Wakko has a gag bag that he takes with him wherever he goes (which is usually hiding somewhere withing the netherams of his shirt.).  It contains anything the Warners will ever need in any situation, i.e. a "potty."
      Wakko is shorter than his brother, closer to the height of Dot so he is approx. 4'5" tall and because all cartoon characters seem to weigh almost nothing we assume he weighs about 5-10 pounds. We think he's pretty close in weight to his older brother due to the fact that he eats so much. Although he shares the same lust for women as Yakko he's a little more innocent about it. He is approx. 9-11 yrs. old
Where did I find some of this great info?
                     Click here:
The Animaniacs Bible
Meet Yakko Warner
Meet Dot Warner
Meet
Wakko
   Warner