The robotic arm is supposed to look small, and child-proportioned, and while the hand looked right, the arm didn't. So I slimmed down the arm part significantly. I also thickened the outlines around the entire arm, to help make it seem closer to Brendan, and help it seem small instead of just distant.
It still wasn't sitting quite right with me, though, and I realized that if I included Brendan's hand the difference in scale would be more obvious. So I added his hand in, and with a prop (the pencil) included everything seemed to snap into an easier-to-grasp scale.
So there you go! Haven't had to make an after-the-fact edit in a while, but I think it works much better.