Edward is Edward! I mean, Tedd's dad!
It was very important to me that Grace move to the front of the sofa by climbing over the top of it. There isn't some big, important reason she had to move. I just thought of her doing it, and concluded "yes."
"That must happen."
I hope this explanation is unnecessary, but in case it is necessary, Tedd and Grace say "yes" in the last panel, and Tedd alone says the last thing. Arguably, I shouldn't have had Grace climb over the sofa to make it easier to arrange the text clearly.
But then Grace wouldn't have climbed over the sofa.