The minor characters(Roy, Shermy, 5, ect.) never really had much of a personality. The stronger personalitied characters (Charlie Brown, Lucy, Linus, Snoopy, Sally, Schroeder, Patricia “Peppermint Patty” Reichardt, Marcie ) were much more interesting than a flat person or thing need only for background extras or a line now and then if the particular line is in contrast to all the personalities of the other stronger types. Of course, as we watch these characters be introduced, we will also watch them grow. And as they grow, we find their personalities growing also… encompassing so many aspects that a flat, one or two- line character is no longer needed… And as we watch the cast of strongers grow in number, we can’t help but realize the man behind the board no longer needs a background extra…
Actually it’s because a girl named “Poochie” started calling him that. Since that, no one ever called him Charlie again, just Charlie Brown. See here:http://www.gocomics.com/peanuts/1973/01/07
Yep.