Okay, I'm noticing a trend here. Arthur now seems to just sit directly on Gramps head when talking to him. However in the past, he used to sit on a lamp that was next to Gramps chair but now just sits directly on his head. This leads to a couple of questions.
1. What ever happened to the lamp?
2. Why does the duck sit on his head instead of his lap?
3. At what point in your life does a duck sitting on your head and starting up a conversation with you seem normal?
4. At what point in the future will Gramps go insane from his life in general?

I'm no expert, but sitting on a head seems more much comfortable to me than sitting on a lamp.

There is a man in Terry Pratchett books the other characters call Duckman who has a duck on his head. He figures he's sane just everyone around him isn't for suggesting there is a duck on his head when of course there couldn't be.

I suspect Gramps has slipped past the point of thinking it's strange but every now and then realises how weird it all is.