re: Why Do Sitcoms Always Have a Token Dumb, Borderline Retarded Character

Shows evolve to get more laughs as the actors find their characters. The first few episodes of Always Sunny, Charlie was basically a normal not terribly bright dude. By season 4 he was a huffing glue and completely illiterate. The funny thing is they have laid several hints that beneath the surface charlie is possibly some type of idiot savant genius. Lots of similarities with Kramer on Seinfeld.