"Kermit is the star, leading frog and emcee of the Muppets. Already a legend of stage, screen and television, Kermit is excited to enter the world of digital entertainment, even if the Muppet Labs' Digitizer does make him turn green. He's used to that by now."
Every Muppet has different things that they like. For every unique object that they like that's placed on the stage, the Muppets's happiness will increase by one (in other words, placing two of the same liked item will still only increase happiness by one ).