I don’t know

Grandboy: Gwumpa, what is that (on video game)?

Me (looking up): O i don’t know.

Grandboy (frustrated, moves the character about):

Grumpa, what is THAT? (points to the same thing)

Me: I don’t know.

Grandboy: Huh? What do you mean, “I don’t know”?

Me: Means I don’t know…

Grandboy: Why don’t you know, Gwumpa?

Me (not resisting the urge at all): I don’t know

Grandboy: AAAAAGHHHHH