Ralph Wiggum is the son of Police Chief Wiggum. 
 
He's the most nerdy and odd character in the show. He goes to Spriengfield's Elementary School and he's in Lisa Simpsons' class. He always acts strangely, even if we don't know if Ralph is just incredibly childish or incredibly stupid. Non one never knows how he will behave. For example, one time he was queuing, and when his turn arrived, he run away crying 'now I can't queue anymore!'. 
 
In the episode I Love Lisa, Ralph crushes bad on Lisa, who doesn't accept his advances... but in the end they decide to remain friends. 
 
During one of the Treehouse of Horror shows, Ralph had an imaginary friend who was a leprechaun who encouraged Ralph to become an arsonist.
 

In Simpsons Super Spectalcular #11, Stretch Dude recruits Ralph as Gluestick to fat off Fat Tony and his goons while Clobber Girl when she has to bout with the super-flu.  Ralph got his powers by eating so much past in his life, and now he can secrete glue from his hands, feet, and other body parts that would be too gross to mention. His weakness is that he can only produce a limited supply of glue, as much as he ate, but luckly (and digusting for us) he can restock himself by eat the paste he already produced and used.  He can use his glue powers as a web-line, swing from the roof tops of the city.