Zack is learning object permanence. Just now he’s spent a couple of delightful minutes putting Shaun the Sheep on a cupboard shelf, closing the door. Waiting a while, opening the door, smiling, picking up Shaun, closing the door, then opening it again and repeating the process. Ad infinitum. I think he's getting the point that Shaun is still there, even if the door is closed.
Now that this is done, he's taking my black pen, putting it up on the desk out of his sight, but in his reach, waiting a while, then picking it up again and repeating the process.