The muppet show always walked close to "breaking the fourth wall" but generally kept the ruse that they did not know they were in a movie by being in a fictional stage play. The latest muppet movie "The Muppets" (2011) was a slight bit different with blatent breaking of that fourth wall. Breaking the fourth wall basically means the characters are aware that they are in a movie/show and aware of the audience (as a character). I was pleasently surprised that in spite of all this refering to the film conventions they are doing within the dialog, they film still was emotionally engaging (for me anyways). Several of the key human characters are actors in the TV show "The Big Bang Theory" which my brother watches often so I have seen many episodes myself. On that TV show, the characters sometimes refer to the film conventions or character conventions they are currently involved in to break that fourth wall but do it in an intellectual fashion. Jim Parsons who plays Sheldon on The Big Bang Theory played two characters, one of which was the mirror image of Walter, a muppet, during a song where he laments that he is too human to join the muppets. For this reason I wondered if Jim also did Walter's voice but no, Walter was voiced by Peter Linz. From here on, this post has been hijacked by an amazing puppet technique.
Looking up Peter Linz, I find the key character of his career is a sloth and main character named Snook in the children's educational TV show "It's A Big Big World". These over-sized puppets are controlled by several puppeteers at once who are dressed in blue-screen or green-screen colors and then the characters are digitally added to three-dimentional virtual computer sets as displayed live to camera operators and puppeteers. They include a clip from a short called "Sizzling Kung-Fu Mice" and a "making of" clip on the website of the "Wainscott Studios." http://www.wainscottstudios.com/video.html These mice are almost human sized to make all four of their feet out of human puppeteer hands. The cat puppet must be the size of a young elephant. it helps to pause the making-of video when they make the puppeteers show up to get a sense of the size and complexity of these puppets and their set-up.