Arthur found a new spot

Oh, who could that be hiding in there?

It's Arthur! And he's not interested in anything you have to say.

This is my new favorite spot. No, I will not get out. Ever. This is my new home. 

 Hey, Why did you stop paying attention to me? I'm still hiding in here. Pay attention to me!

 Walter is having none of this. He couldn't possibly care less or be more annoyed by Arthur's antics.

But don't worry,  at the end of the day they still love each other.

Or, at the very least, tolerate each other in close proximity to one another.