It was said during the commentary of The Muppets that they wanted to give the penguins a line in lifes a happy song but were told penguins can't talk in the muppet universe. This has been accepted for some time now. However when watching older productions like the muppet show and the muppets go to the movies the penguins were always talking and singing in fully pronounced words. Even as late as muppets tonight the penguins could sing in the martin short episode. So what the heck? And it didn't start with The Muppets either. But why and when did this trend start?