Here's a slight explanation:
The transparent boundary- the titled 4th wall, in this story the 4th wall is what you think it is but darker, it's something the cartoon universe should never completely cross (I don't mean saying something to the TV screen like "Hey viewers!" or "Careful there are kids watching this!" I mean them literally crossing the wall that seperates the cartoon universe and OUR reality,) If a character crosses this boundary to the out of bounds, they are eternally stuck in a dark wet landscape, not to mention the effects the out of bounds has on their bodies, but that's for another time.
Side note- The wall that seperates the two realities is called the in between, this place is safer than the out of bounds. A character can go here and turn back safely, but once you reach the out of bounds, there is no going back. Once you walk into the out of bounds no matter how many steps, you're stuck.
The staring Eyes- Those eyes represent OUR reality, the TV viewers watching, they don't talk or move because like us humans, the viewers can't change the story or actually talk to the cartoon. Which is why the eyes only stared, that's all they can do.
Technically imagine if a cartoon character (like tintin) crossed this boundary not knowing the consequences, and became stuck forever, unable to get back to their appropriate cartoon universe. Thats how this universe works.