Ok, I was just as confused as you but then did some research and came up with this:
this is actually really deep. Look:
1.) Right before the notebook puppet told the other puppets to write "creative colors" she showed them a board with a wheel of colors; green wasn't on that board, and when one of the puppets wanted to use green, the notebook puppet IMMEDIATELY said "No, Green is NOT a creative color."
2.) When the notebook puppet told the others to look out the window and look "creatively," they couldn't see anything. THEN the notebook puppet put some monocles over HER OWN ONE EYE, and everyone could suddenly "see" what the notebook wanted them to see, through the perspective of the notebook and her one eye.
3.) When one of the puppets actually created something really nice and ORIGINAL and creative--the picture of the clown--the notebook puppet had black ink smeared on the picture to obliterate it.
4.) When things truly got scary, the facade melted away, the kitchen with the tables and the puppets were zoomed out and you could see a hollywood movie set encompassing the kitchen, indicating this is all manufactured by hollywood...ie the indoctrinating media.
5.) Then, as you can see, the puppets started eating the brains and the heart, telling you that the children's creativity and emotions are being taken by the media, "gobbled up." Basically, the message is supposed to be tragically ironic, because the light-hearted facade hides the sinister plot; on the outside, it looks like they're encouraging children to be "creative," so the mood, songs, and atmosphere is innocent and childlike...but the makers of this sketch are trying to tell you that there's something HIDDEN beneath the friendly facade, a dark, evil purpose, which is why the innocence melts away and all you get is puppets eating brains and hearts and the music turns dark. Even your emotions are manipulated; you feel light-hearted at first, and then you feel fear as the evil is exposed underneath the light. THIS is the nature of children's cartoons; the dark beneath the light.
Don't you see? This is the perfect metaphor for how our children are being conditioned by cartoons and children's shows to think a certain way, view things a certain way, AND EVEN OUR EDUCATION IS INDOCTRINATED IN A CERTAIN WAY. The elite create shows to "teach" children to be creative, but in actuality, they're teaching our children to be...puppets.